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27 février 2011 7 27 /02 /février /2011 12:26

A transformer is a static device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondarywinding  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load  Dell Studio XPS 1640 Battery .

In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp), and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np  Dell Vostro 1710 Battery .

In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids  Dell KM958 battery .

All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage   Dell Studio 1555 battery .

Transformers are essential for high-voltage electric power transmission, which makes long-distance transmission economically practical.


The phenomenon of electromagnetic induction was discovered independently by Michael Faraday and Joseph Henry in 1831  Sony VGP-BPS13 battery .

However, Faraday was the first to publish the results of his experiments and thus receive credit for the discovery.The relationship between electromotive force (EMF) or "voltage" and magnetic flux was formalized in an equation now referred to as "Faraday's law of induction"  Sony VGP-BPS13/B battery :

where  is the magnitude of the EMF in volts and ?B is the magnetic flux through the circuit (in webers).

Faraday performed the first experiments on induction between coils of wire, including winding a pair of coils around an iron ring, thus creating the first toroidal closed-core transformer  Sony VGP-BPS13/S battery .

Induction coils

The first type of transformer to see wide use was the induction coil, invented by Rev. Nicholas Callan ofMaynooth College, Ireland in 1836. He was one of the first researchers to realize that the more turns the secondary winding has in relation to the primary winding, the larger is the increase in EMF  Sony VGP-BPS13A/B battery .

Induction coils evolved from scientists' and inventors' efforts to get higher voltages from batteries. Since batteries producedirect current (DC) rather than alternating current (AC), induction coils relied upon vibrating electrical contacts that regularly interrupted the current in the primary to create the flux changes necessary for induction  Sony VGP-BPS13B/B battery .

Between the 1830s and the 1870s, efforts to build better induction coils, mostly by trial and error, slowly revealed the basic principles of transformers  Sony VGP-BPL9 battery .

In 1876, Russian engineer Pavel Yablochkov invented a lighting system based on a set of induction coils where the primary windings were connected to a source of alternating current and the secondary windings could be connected to several "electric candles" (arc lamps) of his own design  Sony VGP-BPS13B/B battery .

The coils Yablochkov employed functioned essentially as transformers.

In 1878, the Ganz Company in Hungary began manufacturing equipment for electric lighting and, by 1883, had installed over fifty systems in Austria-Hungary       Sony VGP-BPL15 battery .

Their systems used alternating current exclusively and included those comprising both arc and incandescent lamps, along with generators and other equipment.

Lucien Gaulard and John Dixon Gibbs first exhibited a device with an open iron core called a "secondary generator" in London in 1882, then sold the idea to the Westinghouse company in the United States  Dell Inspiron E1505 battery .

They also exhibited the invention in Turin, Italy in 1884, where it was adopted for an electric lighting system. However, the efficiency of their open-core bipolar apparatus remained very low.

Induction coils with open magnetic circuits are inefficient for transfer of power to loads  Dell Latitude E6400 battery .

Until about 1880, the paradigm for AC power transmission from a high voltage supply to a low voltage load was a series circuit. Open-core transformers with a ratio near 1:1 were connected with their primaries in series to allow use of a high voltage for transmission while presenting a low voltage to the lamps  HP Pavilion dv6000 Battery .

The inherent flaw in this method was that turning off a single lamp affected the voltage supplied to all others on the same circuit. Many adjustable transformer designs were introduced to compensate for this problematic characteristic of the series circuit, including those employing methods of adjusting the core or bypassing the magnetic flux around part of a coil SONY VAIO VGN-FZ Battery .

Efficient, practical transformer designs did not appear until the 1880s, but within a decade the transformer would be instrumental in the "War of Currents", and in seeing AC distribution systems triumph over their DC counterparts, a position in which they have remained dominant ever since  SONY VAIO VGN-FZ18 Battery .

Closed-core lighting transformers

In the autumn of 1884 , Ganz Company engineers Károly Zipernowsky, Ottó Bláthy and Miksa Déri had determined that open-core devices were impracticable, as they were incapable of reliably regulating voltage. In their joint patent application for the "Z.B.DSONY VAIO VGN-FZ21E Battery .

" transformers, they described two designs with closed magnetic circuits: the "closed-core" and "shell-core" transformers. In the closed-core, the primary and secondary windings were wound around a closed iron ring; in the shell-core, the windings were passed through the iron core SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

In both designs, the magnetic flux linking the primary and secondary windings traveled almost entirely within the iron core, with no intentional path through air. The new Z.B.D. transformers reached 98 percent efficiency, which was 3.4 times higher than the open core bipolar devices of Gaulard and Gibs SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

When employed in parallel connected electric distribution systems, closed-core transformers finally made it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces. Bláthy had suggested the use of closed-cores, Zipernowsky the use of shunt connections, and Déri had performed the experiments SONY VAIO VGN-FW21E Battery ;

Bláthy also discovered the transformer formula, Vs/Vp = Ns/Np.[citation needed] The vast majority of transformers in use today rely on the basic principles discovered by the three engineers. They also reportedly popularized the word "transformer" to describe a device for altering the EMF of an electric current,although the term had already been in use by 1882  SONY VAIO VGN-NR11S/S Battery .

In 1886, the Ganz Company installed the world's first power station that used AC generators to power a parallel-connected common electrical network, the steam-powered Rome-Cerchi power plant  SONY VAIO VGN-NR11M/S Battery .

Although George Westinghouse had bought Gaulard and Gibbs' patents in 1885, the Edison Electric Light Company held an option on the U.S. rights for the Z.B.D. transformers, requiring Westinghouse to pursue alternative designs on the same principles  SONY VAIO VGN-NR11Z/S Battery .

He assigned to William Stanley the task of developing a device for commercial use in United States. Stanley's first patented design was for induction coils with single cores of soft iron and adjustable gaps to regulate the EMF present in the secondary winding. (See drawing at left  SONY VAIO VGN-NR11Z/T Battery .)

This design was first used commercially in the U.S. in 1886. But Westinghouse soon had his team working on a design whose core comprised a stack of thin "E-shaped" iron plates, separated individually or in pairs by thin sheets of paper or other insulating material  Sony VAIO VGN-FZ21E Battery .

Prewound copper coils could then be slid into place, and straight iron plates laid in to create a closed magnetic circuit. Westinghouse applied for a patent for the new design in December 1886; it was granted in July 1887  Sony VAIO VGN-FW21E Battery .

Other early transformers

In 1889, Russian-born engineer Mikhail Dolivo-Dobrovolsky developed the first three-phase transformer at the Allgemeine Elektricitäts-Gesellschaft ("General Electricity Company") in Germany  Sony VAIO VGN-NR11S/S Battery .

In 1891, Nikola Tesla invented the Tesla coil, an air-cored, dual-tuned resonant transformer for generating very high voltages at high frequency.

Audio frequency transformers ("repeating coils") were used by early experimenters in the development of the telephone  Sony VAIO VGN-NR11Z/S Battery .

Basic principles

The transformer is based on two principles: first, that an electric current can produce a magnetic field (electromagnetism), and, second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction)Sony VAIO VGN-NR11M/S Battery .

Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.

An ideal transformer

An ideal transformer is shown in the adjacent figure. Current passing through the primary coil creates a magnetic field  Sony VAIO VGN-NR11Z/T Battery .

The primary and secondary coils are wrapped around a core of very high magnetic permeability, such as iron, so that most of the magnetic flux passes through both the primary and secondary coils  SONY VAIO VGN-FZ180E Battery .

Induction law

The voltage induced across the secondary coil may be calculated from Faraday's law of induction, which states that

where Vs is the instantaneous voltage, Ns is the number of turns in the secondary coil and ? is the magnetic flux through one turn of the coil  SONY VAIO VGN-FZ220E Battery .

If the turns of the coil are oriented perpendicular to the magnetic field lines, the flux is the product of the magnetic flux density B and the area A through which it cuts. The area is constant, being equal to the cross-sectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary  SONY VAIO VGN-FZ340E Battery .

Since the same magnetic flux passes through both the primary and secondary coils in an ideal transformer, the instantaneous voltage across the primary winding equals Taking the ratio of the two equations for Vs and Vp gives the basic equation  for stepping up or stepping down the voltage  SONY VAIO VGN-FZ430E Battery .

Np/Ns is known as the turns ratio, and is the primary functional characteristic of any transformer. In the case of step-up transformers, this may sometimes be stated as the reciprocal, Ns/Np. Turns ratio is commonly expressed as an irreducible fraction or ratio  SONY VAIO VGN-FZ460E Battery :

for example, a transformer with primary and secondary windings of, respectively, 100 and 150 turns is said to have a turns ratio of 2:3 rather than 0.667 or 100:150   SONY VAIO VGN-FZ480E Battery .

Ideal power equation

If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit   SONY VAIO VGN-FZ4000 Battery .

Ideally, the transformer is perfectly efficient; all the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the incoming electric power must equal the outgoing power  SONY VAIO VGN-FZ31E Battery :

Transformers normally have high efficiency, so this formula is a reasonable approximation.

If the voltage is increased, then the current is decreased by the same factor. The impedance in one circuit is transformed by the square of the turns ratio  SONY VAIO VGN-FZ31B Battery .

For example, if an impedance Zs is attached across the terminals of the secondary coil, it appears to the primary circuit to have an impedance of (Np/Ns)2Zs. This relationship is reciprocal, so that the impedance Zp of the primary circuit appears to the secondary to be (Ns/Np)2Zp  SONY VAIO VGN-FZ31J Battery .

Detailed operation

The simplified description above neglects several practical factors, in particular the primary current required to establish a magnetic field in the core, and the contribution to the field due to current in the secondary circuit  SONY VAIO VGN-FZ31M Battery .

Models of an ideal transformer typically assume a core of negligible reluctance with two windings of zero resistance.When a voltage is applied to the primary winding, a small current flows, driving flux around the magnetic circuit of the core.The current required to create the flux is termed the magnetizing current  SONY VAIO VGN-FZ31M Battery ;

since the ideal core has been assumed to have near-zero reluctance, the magnetizing current is negligible, although still required to create the magnetic field.

The changing magnetic field induces an electromotive force (EMF) across each winding  SONY VAIO VGN-FZ31Z Battery .

Since the ideal windings have no impedance, they have no associated voltage drop, and so the voltages VP and VS measured at the terminals of the transformer, are equal to the corresponding EMFs. The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the "back EMF"  SONY VAIO VGN-FZ38M Battery .

This is due to Lenz's law which states that the induction of EMF would always be such that it will oppose development of any such change in magnetic field.

Leakage flux

The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself  SONY VGP-BPS8 Battery .

In practice, some flux traverses paths that take it outside the windings. Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings.Leakage results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply  SONY VGP-BPS13/S Battery .

It is not directly a power loss (see "Stray losses" below), but results in inferior voltage regulation, causing the secondary voltage to fail to be directly proportional to the primary, particularly under heavy load. Transformers are therefore normally designed to have very low leakage inductance  SONY VGP-BPS13A/B Battery .

However, in some applications, leakage can be a desirable property, and long magnetic paths, air gaps, or magnetic bypass shunts may be deliberately introduced to a transformer's design to limit the short-circuit current it will supply. Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs  SONY VGP-BPS13B/B Battery ,

mercury vapor lamps, and neon signs; or for safely handling loads that become periodically short-circuited such as electric arc welders.

Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a direct current flowing through the windings  SONY VGP-BPS13A/S Battery .

Leakage inductance is also helpful when transformers are operated in parallel. It can be shown that if the "per-unit" inductance of two transformers is the same (a typical value is 5%), they will automatically split power "correctly" (e.g. 500 kVA unit in parallel with 1,000 kVA unit, the larger one will carry twice the current)  SONY VGP-BPS13AS Battery .

Effect of frequency

If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage Erms of the winding , and the supply frequency f, number of turns N, core cross-sectional area a and peak magnetic flux density B is given by the universal EMF equation  Dell Inspiron 1320n Battery :

If the flux does not contain even harmonics the following equation can be used for half-cycle average voltage Eavg of any waveshape:

The time-derivative term in Faraday's Law shows that the flux in the core is the integral with respect to time of the applied voltageDell Inspiron 1464 Battery .

Hypothetically an ideal transformer would work with direct-current excitation, with the core flux increasing linearly with time.In practice, the flux would rise to the point where magnetic saturation of the core occurs, causing a huge increase in the magnetizing current and overheating the transformer  Dell Inspiron 1564 Battery .

All practical transformers must therefore operate with alternating (or pulsed) current.

The EMF of a transformer at a given flux density increases with frequency. By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance  Dell Inspiron 1764 Battery .

However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight   Dell Studio 1450 Battery .

Conversely, frequencies used for some railway electrification systems were much lower (e.g. 16.7 Hz and 25 Hz) than normal utility frequencies (50 – 60 Hz) for historical reasons concerned mainly with the limitations of early electric traction motors  Dell Studio 1457 Battery .

As such, the transformers used to step down the high over-head line voltages (e.g. 15 kV) are much heavier for the same power rating than those designed only for the higher frequencies.

Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing currentDell Latitude D610 Battery ;

at lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical  Toshiba NB100 Battery .

For example, transformers may need to be equipped with "volts per hertz" over-excitation relays to protect the transformer from overvoltage at higher than rated frequency  Toshiba Satellite M65 battery .

One example of state-of-the-art design is those transformers used for electric multiple unit high speed trains, particularly those required to operate across the borders of countries using different standards of electrification. The position of such transformers is restricted to being hung below the passenger compartment  Toshiba Satellite M60 battery .

They have to function at different frequencies (down to 16.7 Hz) and voltages (up to 25 kV) whilst handling the enhanced power requirements needed for operating the trains at high speed.

Knowledge of natural frequencies of transformer windings is of importance for the determination of the transient response of the windings to impulse and switching surge voltages Dell Latitude D830 Battery .

Energy losses

An ideal transformer would have no energy losses, and would be 100% efficient. In practical transformers energy is dissipated in the windings, core, and surrounding structures   Dell Latitude D620 Battery .

Larger transformers are generally more efficient, and those rated for electricity distribution usually perform better than 98%.

Experimental transformers using superconducting windings achieve efficiencies of 99.85%   Dell Inspiron Mini 10 Battery .

The increase in efficiency can save considerable energy, and hence money, in a large heavily-loaded transformer; the trade-off is in the additional initial and running cost of the superconducting design.

Losses in transformers (excluding associated circuitry) vary with load current, and may be expressed as "no-load" or "full-load" lossSony VGN-FW11S Battery .

Winding resistance dominates load losses, whereas hysteresis and eddy currents losses contribute to over 99% of the no-load loss. The no-load loss can be significant, so that even an idle transformer constitutes a drain on the electrical supply and a running costSony VGN-FW11M Battery ;

designing transformers for lower loss requires a larger core, good-quality silicon steel, or even amorphous steel, for the core, and thicker wire, increasing initial cost, so that there is a trade-off between initial cost and running cost. (Also see energy efficient transformer)  Sony VGN-FW139E/H battery .

Transformer losses are divided into losses in the windings, termed copper loss, and those in the magnetic circuit, termed iron loss. Losses in the transformer arise from   Dell Latitude E5400 Battery :

Winding resistance

Current flowing through the windings causes resistive heating of the conductors. At higher frequencies, skin effect and proximity effect create additional winding resistance and losses  Dell Latitude E4200 Battery .

Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected  Dell Inspiron 300M Battery .

Eddy currents

Ferromagnetic materials are also good conductors, and a core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material   Dell Vostro A840 Battery .

The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness.  Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores  Dell Studio 1737 battery .


Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction. This produces the buzzing sound commonly associated with transformers, and can cause losses due to frictional heating  Dell Inspiron E1505 battery .

Mechanical losses

In addition to magnetostriction, the alternating magnetic field causes fluctuating forces between the primary and secondary windings. These incite vibrations within nearby metalwork, adding to the buzzing noise, and consuming a small amount of power Dell RM791 battery .

Stray losses

Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle  Dell XPS M1530 battery .

However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat. There are also radiative losses due to the oscillating magnetic field, but these are usually small  Dell XPS M2010 battery .

Dot convention

It is common in transformer schematic symbols for there to be a dot at the end of each coil within a transformer, particularly for transformers with multiple primary and secondary windings  Acer Aspire One battery .

The dots indicate the direction of each winding relative to the others. Voltages at the dot end of each winding are in phase; current flowing into the dot end of a primary coil will result in current flowing out of the dot end of a secondary coil  Toshiba Satellite P10 Battery .

Equivalent circuit

The physical limitations of the practical transformer may be brought together as an equivalent circuit model (shown below) built around an ideal lossless transformer  SONY VGN-FZ210CE Battery .

Power loss in the windings is current-dependent and is represented as in-series resistances Rp and Rs. Flux leakage results in a fraction of the applied voltage dropped without contributing to the mutual coupling, and thus can be modeled as reactances of each leakage inductance Xp and Xs in series with the perfectly coupled region  Dell Precision M70 Battery .

Iron losses are caused mostly by hysteresis and eddy current effects in the core, and are proportional to the square of the core flux for operation at a given frequency. Since the core flux is proportional to the applied voltage, the iron loss can be represented by a resistance RC in parallel with the ideal transformer  Toshiba Satellite L305 Battery .

A core with finite permeability requires a magnetizing current Im to maintain the mutual flux in the core. The magnetizing current is in phase with the flux; saturation effects cause the relationship between the two to be non-linear, but for simplicity this effect tends to be ignored in most circuit equivalents  Toshiba Satellite T4900 Battery .

With a sinusoidal supply, the core flux lags the induced EMF by 90° and this effect can be modeled as a magnetizing reactance (reactance of an effective inductance) Xm in parallel with the core loss component. Rc and Xm are sometimes together termed the magnetizing branch of the model  Toshiba PA3399U-2BRS battery .

If the secondary winding is made open-circuit, the current I0 taken by the magnetizing branch represents the transformer's no-load current.

The secondary impedance Rs and Xs is frequently moved (or "referred") to the primary side after multiplying the components by the impedance scaling factor (Np/Ns)2  Toshiba Satellite A200 Battery .

The resulting model is sometimes termed the "exact equivalent circuit", though it retains a number of approximations, such as an assumption of linearity.Analysis may be simplified by moving the magnetizing branch to the left of the primary impedance, an implicit assumption that the magnetizing current is low  Toshiba Satellite 1200 Battery ,

and then summing primary and referred secondary impedances, resulting in so-called equivalent impedance.

The parameters of equivalent circuit of a transformer can be calculated from the results of two transformer tests: open-circuit test and short-circuit test  Toshiba Satellite M300 Battery .


A wide variety of transformer designs are used for different applications, though they share several common features. Important common transformer types include:


In an autotransformer portions of the same winding act as both the primary and secondary  SONY VGP-BPS13A/Q Battery .

The winding has at least three taps where electrical connections are made. An autotransformer can be smaller, lighter and cheaper than a standard dual-winding transformer however the autotransformer does not provide electrical isolation  SONY VGP-BPS13A/Q Battery .

Autotransformers are often used to step up or down between voltages in the 110-117-120 volt range and voltages in the 220-230-240 volt range, e.g., to output either 110 or 120V (with taps) from 230V input, allowing equipment from a 100 or 120V region to be used in a 230V region  SONY VGP-BPS13B/Q Battery .

A variable autotransformer is made by exposing part of the winding coils and making the secondary connection through a sliding brush, giving a variable turns ratio. Such a device is often referred to by the trademark name variac  SONY VGP-BPS13B/Q Battery .

Polyphase transformers

For three-phase supplies, a bank of three individual single-phase transformers can be used, or all three phases can be incorporated as a single three-phase transformer. In this case, the magnetic circuits are connected together, the core thus containing a three-phase flow of flux  SONY VGP-BPS13/Q Battery .

A number of winding configurations are possible, giving rise to different attributes and phase shifts. One particular polyphase configuration is the zigzag transformer, used for grounding and in the suppression of harmonic currents   SONY VGP-BPS13/Q Battery.

Leakage transformers

A leakage transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by a magnetic bypass or shunt in its core between primary and secondary, which is sometimes adjustable with a set screw      SONY VGP-BPS21A/B Battery .

This provides a transformer with an inherent current limitation due to the loose coupling between its primary and the secondary windings. The output and input currents are low enough to prevent thermal overload under all load conditions—even if the secondary is shorted  SONY VGP-BPS21/S Battery .

Leakage transformers are used for arc welding and high voltage discharge lamps (neon lights and cold cathode fluorescent lamps, which are series-connected up to 7.5 kV AC). It acts then both as a voltage transformer and as a magnetic ballast.

Other applications are short-circuit-proof extra-low voltage transformers for toys or doorbell installations  SONY VGP-BPS21B Battery .

Resonant transformers

For more details on this topic, see Resonant inductive coupling.

A resonant transformer is a kind of leakage transformer. It uses the leakage inductance of its secondary windings in combination with external capacitors, to create one or more resonant circuits  SONY VGP-BPS21A Battery .

Resonant transformers such as the Tesla coil can generate very high voltages, and are able to provide much higher current than electrostatic high-voltage generation machines such as the Van de Graaff generator. One of the applications of the resonant transformer is for the CCFL inverter  SONY VGP-BPS21 Battery .

Another application of the resonant transformer is to couple between stages of a superheterodyne receiver, where the selectivity of the receiver is provided by tuned transformers in the intermediate-frequency amplifiers.

Audio transformers

Audio transformers are those specifically designed for use in audio circuits  Sony VGP-BPS21A/B Battery .

They can be used to block radio frequency interference or the DC component of an audio signal, to split or combine audio signals, or to provide impedance matching between high and low impedance circuits, such as between a high impedance tube (valve) amplifier output and a low impedance loudspeaker   Sony VGP-BPS21/S Battery ,

or between a high impedance instrument output and the low impedance input of a mixing console.

Such transformers were originally designed to connect different telephone systems to one another while keeping their respective power supplies isolated, and are still commonly used to interconnect professional audio systems or system components r  Sony VGP-BPS21A Battery .

Being magnetic devices, audio transformers are susceptible to external magnetic fields such as those generated by AC current-carrying conductors. "Hum" is a term commonly used to describe unwanted signals originating from the "mains" power supply (typically 50 or 60 Hz)  Sony VGP-BPS21 Battery .

Audio transformers used for low-level signals, such as those from microphones, often include shielding to protect against extraneous magnetically coupled signals.

Instrument transformers

Instrument transformers are used for measuring voltage and current in electrical power systems, and for power system protection and control  Sony Vaio PCG-5G2L Battery .

Where a voltage or current is too large to be conveniently used by an instrument, it can be scaled down to a standardized, low value. Instrument transformers isolate measurement, protection and control circuitry from the high currents or voltages present on the circuits being measured or controlled  Sony Vaio PCG-5G3L Battery .

A current transformer is a transformer designed to provide a current in its secondary coil proportional to the current flowing in its primary coil.

Voltage transformers (VTs), also referred to as "potential transformers" (PTs), are designed to have an accurately known transformation ratio in both magnitude and phase, over a range of measuring circuit impedances  Sony Vaio PCG-5J1L Battery .

A voltage transformer is intended to present a negligible load to the supply being measured. The low secondary voltage allows protective relay equipment and measuring instruments to be operated at a lower voltages.

Both current and voltage instrument transformers are designed to have predictable characteristics on overloads  Sony Vaio PCG-5K2L Battery .

Proper operation of over-current protective relays requires that current transformers provide a predictable transformation ratio even during a short-circuit.


Transformers can be classified in many different ways; an incomplete list is   Sony Vaio PCG-5J2L Battery :

By power capacity: from a fraction of a volt-ampere (VA) to over a thousand MVA;

By frequency range: power-, audio-, or radio frequency;

By voltage class: from a few volts to hundreds of kilovolts;

By cooling type: air-cooled, oil-filled, fan-cooled, or water-cooled  Sony Vaio PCG-5K1L Battery ;

By application: such as power supply, impedance matching, output voltage and current stabilizer, or circuit isolation;

By purpose: distribution, rectifier, arc furnace, amplifier output, etc.;

By winding turns ratio: step-up, step-down, isolating with equal or near-equal ratio, variable, multiple windings Sony Vaio PCG-6S2L Battery .

Laminated steel cores

Transformers for use at power or audio frequencies typically have cores made of high permeability silicon steel. The steel has a permeability many times that of free space, and the core thus serves to greatly reduce the magnetizing current, and confine the flux to a path which closely couples the windings  Sony Vaio PCG-6S3L Battery .

Early transformer developers soon realized that cores constructed from solid iron resulted in prohibitive eddy-current losses, and their designs mitigated this effect with cores consisting of bundles of insulated iron wires.Later designs constructed the core by stacking layers of thin steel laminations, a principle that has remained in use  Sony Vaio PCG-6V1L Battery .

Each lamination is insulated from its neighbors by a thin non-conducting layer of insulation. The universal transformer equation indicates a minimum cross-sectional area for the core to avoid saturation.

The effect of laminations is to confine eddy currents to highly elliptical paths that enclose little flux, and so reduce their magnitudeSony Vaio PCG-6W1L Battery .

Thinner laminations reduce losses, but are more laborious and expensive to construct.Thin laminations are generally used on high frequency transformers, with some types of very thin steel laminations able to operate up to 10 kHz  Sony Vaio PCG-6W2L Battery .

One common design of laminated core is made from interleaved stacks of E-shaped steel sheets capped with I-shaped pieces, leading to its name of "E-I transformer". Such a design tends to exhibit more losses, but is very economical to manufacture  Sony Vaio PCG-6W3L Battery .

The cut-core or C-core type is made by winding a steel strip around a rectangular form and then bonding the layers together. It is then cut in two, forming two C shapes, and the core assembled by binding the two C halves together with a steel strap. They have the advantage that the flux is always oriented parallel to the metal grains, reducing reluctance  Sony Vaio PCG-7111L Battery .

A steel core's remanence means that it retains a static magnetic field when power is removed. When power is then reapplied, the residual field will cause a high inrush current until the effect of the remaining magnetism is reduced, usually after a few cycles of the applied alternating current  Sony Vaio PCG-7112L Battery .

Overcurrent protection devices such as fuses must be selected to allow this harmless inrush to pass. On transformers connected to long, overhead power transmission lines, induced currents due to geomagnetic disturbances during solar storms can cause saturation of the core and operation of transformer protection devices  Sony Vaio PCG-7113L Battery .

Distribution transformers can achieve low no-load losses by using cores made with low-loss high-permeability silicon steel or amorphous (non-crystalline) metal alloy. The higher initial cost of the core material is offset over the life of the transformer by its lower losses at light load  Sony Vaio PCG-7133L Battery .

Solid cores

Powdered iron cores are used in circuits (such as switch-mode power supplies) that operate above main frequencies and up to a few tens of kilohertz. These materials combine high magnetic permeability with high bulk electrical resistivity  Sony Vaio PCG-7Z2L Battery .

For frequencies extending beyond the VHF band, cores made from non-conductive magnetic ceramic materials called ferrites are common. Some radio-frequency transformers also have movable cores (sometimes called 'slugs') which allow adjustment of the coupling coefficient (and bandwidth) of tuned radio-frequency circuits  Sony Vaio PCG-8Y1L Battery .

Toroidal cores

Toroidal transformers are built around a ring-shaped core, which, depending on operating frequency, is made from a long strip of silicon steel or permalloy wound into a coil, powdered iron, or ferrite  Sony Vaio PCG-8Y2L Battery .

A strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. The closed ring shape eliminates air gaps inherent in the construction of an E-I core.The cross-section of the ring is usually square or rectangular, but more expensive cores with circular cross-sections are also available  Sony Vaio PCG-8Z1L Battery.

The primary and secondary coils are often wound concentrically to cover the entire surface of the core. This minimizes the length of wire needed, and also provides screening to minimize the core's magnetic field from generating electromagnetic interference Sony Vaio PCG-8Z2L Battery .

Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level. Other advantages compared to E-I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers)   SONY VAIO VGN-FW31J Battery ,

lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see "Classification" above)  SONY VAIO VGN-FW31E Battery .

Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E-I types.

Ferrite toroidal cores are used at higher frequencies, typically between a few tens of kilohertz to hundreds of megahertz, to reduce losses, physical size, and weight of switch-mode power supplies   SONY VAIO VGN-FW31B Battery .

A drawback of toroidal transformer construction is the higher labor cost of winding. This is because it is necessary to pass the entire length of a coil winding through the core aperture each time a single turn is added to the coil. As a consequence, toroidal transformers are uncommon above ratings of a few kVA  SONY VAIO VGN-FW31M Battery .

Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containing primary and secondary windings.

Air cores

A physical core is not an absolute requisite and a functioning transformer can be produced simply by placing the windings near each other, an arrangement termed an "air-core" transformer  SONY VAIO VGN-FW31Z Battery .

The air which comprises the magnetic circuit is essentially lossless, and so an air-core transformer eliminates loss due to hysteresis in the core material.The leakage inductance is inevitably high, resulting in very poor regulation, and so such designs are unsuitable for use in power distribution  SONY VAIO VGN-FW38M Battery .

They have however very high bandwidth, and are frequently employed in radio-frequency applications,  for which a satisfactory coupling coefficient is maintained by carefully overlapping the primary and secondary windings. They're also used for resonant transformers such as Tesla coils where they can achieve reasonably low loss in spite of the high leakage inductance SONY VAIO VGN-AW41JF Battery .


Cut view through transformer windings. White: insulator. Green spiral: Grain oriented silicon steel. Black: Primary winding made of oxygen-free copper. Red: Secondary winding. Top left: Toroidal transformer. Right: C-core, but E-core would be similar SONY VAIO VGN-AW41JF/H Battery .

The black windings are made of film. Top: Equally low capacitance between all ends of both windings. Since most cores are at least moderately conductive they also need insulation. Bottom: Lowest capacitance for one end of the secondary winding needed for low-power high-voltage transformers  SONY VAIO VGN-AW41MF Battery .

Bottom left: Reduction of leakage inductance would lead to increase of capacitance.

The conducting material used for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn  SONY VAIO VGN-AW41MF/H Battery .

For small power and signal transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire, such as Formvar wire. Larger power transformers operating at high voltages may be wound with copper rectangular strip conductors insulated by oil-impregnated paper and blocks of pressboard SONY VAIO VGN-AW41XH Battery .

High-frequency transformers operating in the tens to hundreds of kilohertz often have windings made of braided Litz wire to minimize the skin-effect and proximity effect losses. Large power transformers use multiple-stranded conductors as well, since even at low power frequencies non-uniform distribution of current would otherwise exist in high-current windings SONY VAIO VGN-AW41XH/Q Battery .

Each strand is individually insulated, and the strands are arranged so that at certain points in the winding, or throughout the whole winding, each portion occupies different relative positions in the complete conductor. The transposition equalizes the current flowing in each strand of the conductor, and reduces eddy current losses in the winding itself SONY VAIO VGN-AW41ZF Battery .

The stranded conductor is also more flexible than a solid conductor of similar size, aiding manufacture.

For signal transformers, the windings may be arranged in a way to minimize leakage inductance and stray capacitance to improve high-frequency response   SONY VAIO VGN-AW41ZF/B Battery .

This can be done by splitting up each coil into sections, and those sections placed in layers between the sections of the other winding. This is known as a stacked type or interleaved winding  SONY VAIO VGN-AW51JGB Battery .

Both the primary and secondary windings on power transformers may have external connections, called taps, to intermediate points on the winding to allow selection of the voltage ratio. In distribution transformers the taps may be connected to an automatic on-load tap changer for voltage regulation of distribution circuits  SONY VAIO VGN-AW52JGB Battery .

Audio-frequency transformers, used for the distribution of audio to public address loudspeakers, have taps to allow adjustment of impedance to each speaker. A center-tapped transformer is often used in the output stage of an audio power amplifier in a push-pull circuit. Modulation transformers in AM transmitters are very similar  SONY VAIO VGN-AW70B/Q Battery .

Certain transformers have the windings protected by epoxy resin. By impregnating the transformer with epoxy under a vacuum, one can replace air spaces within the windings with epoxy, thus sealing the windings and helping to prevent the possible formation of corona and absorption of dirt or water   SONY VAIO VGN-AW71JB Battery .

This produces transformers more suited to damp or dirty environments, but at increased manufacturing cost.


Cut-away view of three-phase oil-cooled transformer. The oil reservoir is visible at the top. Radiative fins aid the dissipation of heatSONY VAIO VGN-AW73FB Battery .

High temperatures will damage the winding insulation. Small transformers do not generate significant heat and are cooled by air circulation and radiation of heat. Power transformers rated up to several hundred kVA can be adequately cooled by natural convective air-cooling, sometimes assisted by fans  SONY VAIO VGN-AW80NS Battery .

In larger transformers, part of the design problem is removal of heat. Some power transformers are immersed in transformer oil that both cools and insulates the windings. The oil is a highly refined mineral oil that remains stable at transformer operating temperature  SONY VAIO VGN-AW80US Battery .

Indoor liquid-filled transformers are required by building regulations in many jurisdictions to use a non-flammable liquid, or to be located in fire-resistant rooms.  Air-cooled dry transformers are preferred for indoor applications even at capacity ratings where oil-cooled construction would be more economical, because their cost is offset by the reduced building construction cost SONY VAIO VGN-AW80S Battery .

The oil-filled tank often has radiators through which the oil circulates by natural convection; some large transformers employ forced circulation of the oil by electric pumps, ai

ded by external fans or water-cooled heat exchangers. Oil-filled transformers undergo prolonged drying processes to ensure that the transformer is completely free of water vapor before the cooling oil is introducedSONY VAIO VGN-AW80DS Battery .

This helps prevent electrical breakdown under load. Oil-filled transformers may be equipped with Buchholz relays, which detect gas evolved during internal arcing and rapidly de-energize the transformer to avert catastrophic failure.  Oil-filled transformers may fail, rupture, and burn, causing power outages and losses  SONY VAIO VGN-AW81JS Battery .

Installations of oil-filled transformers usually includes fire protection measures such as walls, oil containment, and fire-suppression sprinkler systems.

Polychlorinated biphenyls have properties that once favored their use as a coolant, though concerns over their environmental persistence led to a widespread ban on their use  SONY VAIO VGN-AW81YS Battery .

Today, non-toxic, stable silicone-based oils, or fluorinated hydrocarbons may be used where the expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Before 1977, even transformers that were nominally filled only with mineral oils may also have been contaminated with polychlorinated biphenyls at 10-20 ppm  SONY VAIO VGN-AW82DS Battery .

Since mineral oil and PCB fluid mix, maintenance equipment used for both PCB and oil-filled transformers could carry over small amounts of PCB, contaminating oil-filled transformers.

Some "dry" transformers (containing no liquid) are enclosed in sealed, pressurized tanks and cooled by nitrogen or sulfur hexafluoride gas  SONY VAIO VGN-AW82JS Battery .

Experimental power transformers in the 2 MVA range have been built with superconducting windings which eliminates the copper losses, but not the core steel loss. These are cooled by liquid nitrogen or helium  SONY VAIO VGN-AW82YS Battery .

Insulation drying

Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2010)  SONY VAIO VGN-AW83FS Battery .

Construction of oil-filled transformers requires that the insulation covering the windings be thoroughly dried before the oil is introduced. There are several different methods of drying. Common for all is that they are carried out in vacuum environment. The vacuum makes it difficult to transfer energy (heat) to the insulation  SONY VAIO VGN-AW83GS Battery .

For this there are several different methods. The traditional drying is done by circulating hot air over the active part and cycle this with periods of vacuum (hot-air vacuum drying, HAV). More common for larger transformers is to use evaporated solvent which condenses on the colder active part   SONY VAIO VGN-AW83HS Battery .

The benefit is that the entire process can be carried out at lower pressure and without influence of added oxygen. This process is commonly called vapour-phase drying (VPD).

For distribution transformers, which are smaller and have a smaller insulation weight, resistance heating can be used  SONY VAIO VGN-AW90NS Battery .

This is a method where current is injected in the windings to heat the insulation. The benefit is that the heating can be controlled very well and it is energy efficient. The method is called low-frequency heating (LFH) since the current is injected at a much lower frequency than the nominal of the grid, which is normally 50 or 60 Hz   SONY VAIO VGN-AW90S Battery .

A lower frequency reduces the effect of the inductance in the transformer, so the voltage can be reduced.


Very small transformers will have wire leads connected directly to the ends of the coils, and brought out to the base of the unit for circuit connections  SONY VAIO VGN-AW90US Battery .

Larger transformers may have heavy bolted terminals, bus bars or high-voltage insulated bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide careful control of the electric field gradient without letting the transformer leak oil  SONY VAIO VGN-AW91CDS Battery .


Image of an electrical substation in Melbourne, Australia showing 3 of 5 220kV/66kV transformers, each with a capacity of 185MVA

A major application of transformers is to increase voltage before transmitting electrical energy over long distances through wiresSONY VAIO VGN-AW91CJS Battery .

Wires have resistance and so dissipate electrical energy at a rate proportional to the square of the current through the wire. By transforming electrical power to a high-voltage (and therefore low-current) form for transmission and back again afterward, transformers enable economical transmission of power over long distances  SONY VAIO VGN-AW91CYS Battery .

Consequently, transformers have shaped the electricity supply industry, permitting generation to be located remotely from points of demand. All but a tiny fraction of the world's electrical power has passed through a series of transformers by the time it reaches the consumer  SONY VAIO VGN-AW91JS Battery .

Transformers are also used extensively in electronic products to step down the supply voltage to a level suitable for the low voltage circuits they contain. The transformer also electrically isolates the end user from contact with the supply voltage  SONY VAIO VGN-AW91YS Battery .

Signal and audio transformers are used to couple stages of amplifiers and to match devices such as microphones and record players to the input of amplifiers. Audio transformers allowed telephone circuits to carry on a two-way conversation over a single pair of wires  SONY VAIO VGN-AW92CDS Battery .

A balun transformer converts a signal that is referenced to ground to a signal that has balanced voltages to ground, such as between external cables and internal circuits.

The principle of open-circuit (unloaded) transformer is widely used for characterisation of soft magnetic materials, for example in the internationally standardised Epstein frame method  SONY VAIO VGN-AW92CJS Battery .

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26 février 2011 6 26 /02 /février /2011 11:27

An electric motor converts electrical energy into mechanical energy. Most electric motors operate through interacting magnetic fields and current-carrying conductors to generate force, although electrostatic motors use electrostatic forces  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

The reverse process, producing electrical energy from mechanical energy, is done by generators such as an alternator or a dynamo. Many types of electric motors can be run as generators, and vice versa. For example a starter/generator for a gas turbine, or traction motors used on vehicles, often perform both tasks  Dell Studio XPS 1640 Battery .

Electric motors and generators are commonly referred to aselectric machines.

Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives  Dell Vostro 1710 Battery .

They may be powered by direct current (e.g., a battery powered portable device or motor vehicle), or by alternating current from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses  Dell KM958 battery .

The very largest electric motors are used for propulsion of ships, pipeline compressors, and water pumpswith ratings in the millions of watts. Electric motors may be classified by the source of electric power, by their internal construction, by their application, or by the type of motion they give  Dell Studio 1555 battery .

The physical principle of production of mechanical force by the interactions of an electric current and a magnetic field was known as early as 1821. Electric motors of increasing efficiency were constructed throughout the 19th century, but commercial exploitation of electric motors on a large scale required efficientelectrical generators and electrical distribution networks Sony VGP-BPS13 battery .

Some devices, such as magnetic solenoids and loudspeakers, although they generate some mechanical power, are not generally referred to as electric motors, and are usually termed actuators and transducers, respectively Sony VGP-BPS13/B battery .

The principle

The conversion of electrical energy into mechanical energy by a electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet was placed  Sony VGP-BPS13/S battery .

When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine (salt water) is sometimes used in place of the toxic mercury  Sony VGP-BPS13A/B battery .

This is the simplest form of a class of devices called homopolar motors. A later refinement is the Barlow's wheel. These were demonstration devices only, unsuited to practical applications due to their primitive construction.

Jedlik's "electromagnetic self-rotor", 1827 Sony VGP-BPS13B/B battery .

In 1827, Hungarian physicist Ányos Jedlik started experimenting with devices he called "electromagnetic self-rotors". Although they were used only for instructional purposes, in 1828 Jedlik demonstrated the first device to contain the three main components of practical direct current motors: the stator, rotor and commutator  Sony VGP-BPL9 battery .

The device employed no permanent magnets, as the magnetic fields of both the stationary and revolving components were produced solely by the currents flowing through their windings.

The first electric motors

The first commutator-type direct current electric motor capable of turning machinery was invented by the British scientist William Sturgeon in 1832   Sony VGP-BPS13B/B battery .

Following Sturgeon's work, a commutator-type direct-current electric motor made with the intention of commercial use was built by Americans Emily and Thomas Davenport and patented in 1837. Their motors ran at up to 600 revolutions per minute, and powered machine tools and a printing press  Sony VGP-BPL15 battery .

Due to the high cost of the zinc electrodes required by primary battery power, the motors were commercially unsuccessful and the Davenports went bankrupt. Several inventors followed Sturgeon in the development of DC motors but all encountered the same cost issues with primary battery power  Dell Inspiron E1505 battery .

No electricity distribution had been developed at the time. Like Sturgeon's motor, there was no practical commercial market for these motors.

In 1855 Jedlik built a device using similar principles to those used in his electromagnetic self-rotors that was capable of useful workDell Latitude E6400 battery .

He built a model electric motor-propelled vehicle that same year. There is no evidence that this experimentation was communicated to the wider scientific world at that time, or that it influenced the development of electric motors in the following decades  HP Pavilion dv6000 Battery .

The modern DC motor was invented by accident in 1873, when Zénobe Gramme connected the dynamo he had invented to a second similar unit, driving it as a motor. The Gramme machine was the first electric motor that was successful in the industry  SONY VAIO VGN-FZ Battery .

In 1886 Frank Julian Sprague invented the first practical DC motor, a non-sparking motor capable of constant speed under variable loads. Other Sprague electric inventions about this time greatly improved grid electric distribution (prior work done while employed by Thomas Edison)  SONY VAIO VGN-FZ18 Battery ,

allowed power from electric motors to be returned to the electric grid, provided for electric distribution to trolleys via overhead wires and the trolley pole, and provided controls systems for electric operations. This allowed Sprague to use electric motors to invent the first electric trolley system in 1887–88 in Richmond VA  SONY VAIO VGN-FZ21E Battery ,

the electric elevator and control system in 1892, and the electric subway with independently powered centrally controlled cars, which was first installed in 1892 in Chicago by the South Side Elevated Railway where it became popularly known as the "L"  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Sprague's motor and related inventions led to an explosion of interest and use in electric motors for industry, while almost simultaneously another great inventor was developing its primary competitor, which would become much more widespread  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

In 1888 Nikola Tesla invented the first practicable AC motor and with it the polyphase power transmission system. Tesla continued his work on the AC motor in the years to follow at the Westinghouse company  SONY VAIO VGN-FW21E Battery .

The development of electric motors of acceptable efficiency was delayed for several decades by failure to recognize the extreme importance of a relatively small air gap between rotor and stator. Efficient designs have a comparatively small air gap  SONY VAIO VGN-NR11S/S Battery .

The St. Louis motor, long used in classrooms to illustrate motor principles, is extremely inefficient for the same reason, as well as appearing nothing like a modern motor. Photo of a traditional form of the St. Louis motor:

Application of electric motors revolutionized industry  SONY VAIO VGN-NR11M/S Battery .

Industrial processes were no longer limited by power transmission using shaft, belts, compressed air or hydraulic pressure. Instead every machine could be equipped with its own electric motor, providing easy control at the point of use, and improving power transmission efficiency  SONY VAIO VGN-NR11Z/S Battery .

Electric motors applied in agriculture eliminated human and animal muscle power from such tasks as handling grain or pumping water. Household uses of electric motors reduced heavy labor in the home and made higher standards of convenience, comfort and safety possible. Today, electric motors consume more than half of all electric energy produced  SONY VAIO VGN-NR11Z/T Battery .

Categorization of electric motors

The classic division of electric motors has been that of Alternating Current (AC) types vs Direct Current (DC) types. This is more a de facto convention, rather than a rigid distinction. For example, many classic DC motors run on AC power, these motors being referred to as universal motors  Sony VAIO VGN-FZ21E Battery .

Rated output power is also used to categorize motors, those of less than 746 Watts, for example, are often referred to as fractional horsepower motors (FHP) in reference to the old imperial measurement  Sony VAIO VGN-FW21E Battery .

The ongoing trend toward electronic control further muddles the distinction, as modern drivers have moved the commutator out of the motor shell. For this new breed of motor, driver circuits are relied upon to generate sinusoidal AC drive currents, or some approximation thereof   Sony VAIO VGN-NR11S/S Battery .

The two best examples are: the brushless DC motor and the stepping motor, both being poly-phase AC motors requiring external electronic control, although historically, stepping motors (such as for maritime and naval gyrocompass repeaters) were driven from DC switched by contacts  Sony VAIO VGN-NR11Z/S Battery .

Considering all rotating (or linear) electric motors require synchronism between a moving magnetic field and a moving current sheet for average torque production, there is a clearer distinction between an asynchronous motor and synchronous types  Sony VAIO VGN-NR11M/S Battery .

An asynchronous motor requires slip between the moving magnetic field and a winding set to induce current in the winding set by mutual inductance; the most ubiquitous example being the common AC induction motor which must slip to generate torque  Sony VAIO VGN-NR11Z/T Battery .

In the synchronous types, induction (or slip) is not a requisite for magnetic field or current production (e.g. permanent magnet motors, synchronous brush-less wound-rotor doubly-fed electric machine).

DC motors

A DC motor is designed to run on DC electric power  SONY VAIO VGN-FZ180E Battery .

Two examples of pure DC designs are Michael Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to periodically reverse the current in the rotor windings  SONY VAIO VGN-FZ220E Battery .

Permanent-magnet motors

A permanent-magnet motor does not have a field winding on the stator frame, instead relying on permanent magnets to provide the magnetic field against which the rotor field interacts to produce torque  SONY VAIO VGN-FZ340E Battery .

Compensating windings in series with the armature may be used on large motors to improve commuation under load. Because this field is fixed, it cannot be adjusted for speed control. Permanent-magnet motors are convenient in miniature motors to eliminate the power consumption of the field winding   SONY VAIO VGN-FZ430E Battery .

Most larger DC motors are of the "dynamo" type, which requires current to flow in field windings to provide the stator magnetic field.

To minimize overall weight and size, miniature permanent-magnet motors may use high energy magnets made with neodymium or other strategic elements  SONY VAIO VGN-FZ460E Battery .

With the higher flux density provided, electric machines with high energy permanent magnets are at least competitive with all optimally designed singly-fed synchronous and induction electric machines   SONY VAIO VGN-FZ480E Battery .

Brushed DC motors

DC motor design generates an oscillating current in a wound rotor, or armature, with a split ring commutator, and either a wound or permanent magnet stator. A rotor consists of one or more coils of wire wound around a core on a shaft; an electrical power source is connected to the rotor coil through the commutator and its brushes, causing current to flow in it, producing electromagnetism SONY VAIO VGN-FZ4000 Battery .

The commutator causes the current in the coils to be switched as the rotor turns, keeping the magnetic poles of the rotor from ever fully aligning with the magnetic poles of the stator field, so that the rotor never stops (like a compass needle does) but rather keeps rotating indefinitely   SONY VAIO VGN-FZ31E Battery .

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. Sparks are created by the brushes making and breaking circuits through the rotor coils as the brushes cross the insulating gaps between commutator sections  SONY VAIO VGN-FZ31B Battery .

Depending on the commutator design, this may include the brushes shorting together adjacent sections—and hence coil ends—momentarily while crossing the gaps. Furthermore, the inductance of the rotor coils causes the voltage across each to rise when its circuit is opened, increasing the sparking of the brushes  SONY VAIO VGN-FZ31J Battery .

This sparking limits the maximum speed of the machine, as too-rapid sparking will overheat, erode, or even melt the commutator. The current density per unit area of the brushes, in combination with their resistivity, limits the output of the motor. The making and breaking of electric contact also causes electrical noise, and the sparks additionally cause RFI  SONY VAIO VGN-FZ31M Battery .

Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance (on larger motors) or replacement (on small motors). The commutator assembly on a large motor is a costly element, requiring precision assembly of many parts  SONY VAIO VGN-FZ31Z Battery .

On small motors, the commutator is usually permanently integrated into the rotor, so replacing it usually requires replacing the whole rotor.

Large brushes are desired for a larger brush contact area to maximize motor output, but small brushes are desired for low mass to maximize the speed at which the motor can run without the brushes excessively bouncing and sparking (comparable to the problem of "valve float" in internal combustion engines)  SONY VAIO VGN-FZ38M Battery .

(Small brushes are also desirable for lower cost.) Stiffer brush springs can also be used to make brushes of a given mass work at a higher speed, but at the cost of greater friction losses (lower efficiency) and accelerated brush and commutator wear. Therefore, DC motor brush design entails a trade-off between output power, speed, and efficiency/wear SONY VGP-BPS8 Battery .

Brushless DC motors

Some of the problems of the brushed DC motor are eliminated in the brushless design. In this motor, the mechanical "rotating switch" or commutator/brushgear assembly is replaced by an external electronic switch synchronised to the rotor's position  SONY VGP-BPS13/S Battery .

Brushless motors are typically 85–90% efficient or more (higher efficiency for a brushless electric motor of up to 96.5% were reported by researchers at the Tokai University in Japan in 2009), whereas DC motors with brushgear are typically 75–80% efficientSONY VGP-BPS13A/B Battery .

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect sensors to sense the position of the rotor, and the associated drive electronics  SONY VGP-BPS13B/B Battery .

The coils are activated, one phase after the other, by the drive electronics as cued by the signals from either Hall effect sensors or from the back EMF (electromotive force) of the undriven coils. In effect, they act as three-phase synchronous motors containing their own variable-frequency drive electronics  SONY VGP-BPS13A/S Battery .

A specialized class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-controlled vehicles. When configured with the magnets on the outside, these are referred to by modelers as outrunner motors  SONY VGP-BPS13AS Battery .

Brushless DC motors are commonly used where precise speed control is necessary, as in computer disk drives or in video cassette recorders, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as fans, laser printers and photocopiers  Dell Inspiron 1320n Battery .

They have several advantages over conventional motors:

Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan's bearings  Dell Inspiron 1464 Battery .

Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically sensitive devices like audio equipment or computers Dell Inspiron 1564 Battery .

The same Hall effect sensors that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a "fan OK" signal.

The motor can be easily synchronized to an internal or external clock, leading to precise speed control Dell Inspiron 1764 Battery .

Brushless motors have no chance of sparking, unlike brushed motors, making them better suited to environments with volatile chemicals and fuels. Also, sparking generates ozone which can accumulate in poorly ventilated buildings risking harm to occupants' health Dell Studio 1450 Battery .

Brushless motors are usually used in small equipment such as computers and are generally used to get rid of unwanted heat.

They are also very quiet motors which is an advantage if being used in equipment that is affected by vibrations  Dell Studio 1457 Battery .

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-performance electric model aircraft  Dell Latitude D610 Battery .

Coreless or ironless DC motors

Nothing in the principle of any of the motors described above requires that the iron (steel) portions of the rotor actually rotate. If the soft magnetic material of the rotor is made in the form of a cylinder, then (except for the effect of hysteresis) torque is exerted only on the windings of the electromagnets  Toshiba NB100 Battery .

Taking advantage of this fact is the coreless or ironless DC motor, a specialized form of a brush or brushless DC motor. Optimized for rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the form of a winding-filled cylinder, or a self-supporting structure comprising only the magnet wire and the bonding material  Toshiba Satellite M65 battery .

The rotor can fit inside the stator magnets; a magnetically soft stationary cylinder inside the rotor provides a return path for the stator magnetic flux. A second arrangement has the rotor winding basket surrounding the stator magnets. In that design, the rotor fits inside a magnetically soft cylinder that can serve as the housing for the motor, and likewise provides a return path for the fluxToshiba Satellite M60 battery .

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanical time constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper  Dell Latitude D830 Battery .

But because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be cooled by forced air.

Related limited-travel actuators have no core and a bonded coil placed between the poles of high-flux thin permanent magnets. These are the fast head positioners for rigid-disk ("hard disk") drives  Dell Latitude D620 Battery .

Printed armature or pancake DC motors

A rather unusual motor design the pancake/printed armature motor has the windings shaped as a disc running between arrays of high-flux magnets, arranged in a circle, facing the rotor and forming an axial air gap  Dell Inspiron Mini 10 Battery .

This design is commonly known the pancake motor because of its extremely flat profile, although the technology has had many brand names since its inception, such as ServoDisc  Sony VGN-FW11S Battery .

The printed armature (originally formed on a printed circuit board) in a printed armature motor is made from punched copper sheets that are laminated together using advanced composites to form a thin rigid disc. The printed armature has a unique construction, in the brushed motor world, in that it does not have a separate ring commutator  Sony VGN-FW11M Battery .

The brushes run directly on the armature surface making the whole design very compact.

An alternative manufacturing method is to use wound copper wire laid flat with a central conventional commutator, in a flower and petal shape  Sony VGN-FW139E/H battery .

The windings are typically stabilized by being impregnated with electrical epoxy potting systems. These are filled epoxies that have moderate mixed viscosity and a long gel time. They are highlighted by low shrinkage and low exotherm, and are typically UL 1446 recognized as a potting compound for use up to 180°C (Class H) (UL File No. E 210549)  Dell Latitude E5400 Battery .

The unique advantage of ironless DC motors is that there is no cogging (vibration caused by attraction between the iron and the magnets) and parasitic eddy currents cannot form in the rotor as it is totally ironless  Dell Latitude E4200 Battery .

This can greatly improve efficiency, but variable-speed controllers must use a higher switching rate (>40 kHz) or direct current because of the decreased electromagnetic induction.

These motors were originally invented to drive the capstan(s) of magnetic tape drives, in the burgeoning computer industry  Dell Inspiron 300M Battery .

Pancake motors are still widely used in high-performance servo-controlled systems, humanoid robotic systems, industrial automation and medical devices. Due to the variety of constructions now available the technology is used in applications from high temperature military to low cost pump and basic servo applications  Dell Vostro A840 Battery .

Universal motors

A series-wound motor is referred to as a universal motor when it has been designed to operate on either AC or DC power. The ability to operate on AC is because the current in both the field and the armature (and hence the resultant magnetic fields) will alternate (reverse polarity) in synchronism, and hence the resulting mechanical force will occur in a constant direction Dell Studio 1737 battery .

Operating at normal power line frequencies, universal motors are often found in a range rarely larger than 1000 watt. Universal motors also form the basis of the traditional railway traction motor in electric railways  Dell Inspiron E1505 battery .

In this application, the use of AC to power a motor originally designed to run on DC would lead to efficiency losses due to eddy current heating of their magnetic components, particularly the motor field pole-pieces that, for DC, would have used solid (un-laminated) iron  Dell RM791 battery .

Although the heating effects are reduced by using laminated pole-pieces, as used for the cores of transformers and by the use of laminations of high permeability electrical steel, one solution available at start of the 20th century was for the motors to be operated from very low frequency AC supplies, with 25 and 16.7 Hz operation being common  Dell XPS M1530 battery .

Because they used universal motors, locomotives using this design were also commonly capable of operating from a third rail powered by DC.

An advantage of the universal motor is that AC supplies may be used on motors which have some characteristics more common in DC motors, specifically high starting torque and very compact design if high running speeds are used Dell XPS M2010 battery .

The negative aspect is the maintenance and short life problems caused by the commutator. Such motors are used in devices such as food mixers and power tools which are used only intermittently, and often have high starting-torque demands  Acer Aspire One battery .

Continuous speed control of a universal motor running on AC is easily obtained by use of a thyristor circuit, while multiple taps on the field coil provide (imprecise) stepped speed control. Household blenders that advertise many speeds frequently combine a field coil with several taps and a diode that can be inserted in series with the motor Toshiba Satellite P10 Battery .

Induction motors can't turn faster than allowed by the power line frequency. By contrast, universal motors generally run at high speeds, making them useful for appliances such as blenders, vacuum cleaners, and hair dryers where high speed and light weight is desirable      SONY VGN-FZ210CE Battery .

They are also commonly used in portable power tools, such as drills, sanders, circular and jig saws, where the motor's characteristics work well. Many vacuum cleaner and weed trimmer motors exceed 10,000 RPM, while Dremel and other similar miniature grinders will often exceed 30,000 RPM  Dell Precision M70 Battery .

Universal motors also lend themselves to electronic speed control and, as such, are an ideal choice for domestic washing machines. The motor can be used to agitate the drum (both forwards and in reverse) by switching the field winding with respect to the armature. The motor can also be run up to the high speeds required for the spin cycle  Toshiba Satellite L305 Battery .

Motor damage may occur from overspeeding (running at an rotational speed in excess of design limits) if the unit is operated with no significant load. On larger motors, sudden loss of load is to be avoided, and the possibility of such an occurrence is incorporated into the motor's protection and control schemes  Toshiba Satellite T4900 Battery .

In some smaller applications, a fan blade attached to the shaft often acts as an artificial load to limit the motor speed to a safe level, as well as a means to circulate cooling airflow over the armature and field windings.

AC motors

In 1882, Nikola Tesla discovered the rotating magnetic field, and pioneered the use of a rotary field of force to operate machinesToshiba PA3399U-2BRS battery .

He exploited the principle to design a unique two-phase induction motor in 1883. In 1885, Galileo Ferraris independently researched the concept. In 1888, Ferraris published his research in a paper to the Royal Academy of Sciences in Turin.

Tesla had suggested that the commutators from a machine could be removed and the device could operate on a rotary field of forceToshiba Satellite A200 Battery .

Professor Poeschel, his teacher, stated that would be akin to building a perpetual motion machine.  Tesla would later attain U.S. Patent 0,416,194, Electric Motor (December 1889), which resembles the motor seen in many of Tesla's photos. This classic alternating current electro-magnetic motor was an induction motor Toshiba Satellite 1200 Battery .

Michail Osipovich Dolivo-Dobrovolsky later invented a three-phase "cage-rotor" in 1890. This type of motor is now used for the vast majority of commercial applications.

An AC motor has two parts. A stationary stator having coils supplied with AC current to produce a rotating magnetic field, and a rotor attached to the output shaft that is given a torque by the rotating field  Toshiba Satellite M300 Battery .

AC Motor with sliding rotor

Conical rotor brake motor incorporates the brake as an integral part of the conical sliding rotor. When the motor is at rest, a spring acts on the sliding rotor and forces the brake ring against the brake cap in the motor, holding the rotor stationary  SONY VGP-BPS13A/Q Battery .

When the motor is energized, its magnetic field generates both an axial and a radial component. The axial component overcomes the spring force, releasing the brake; while the radial component causes the rotor to turn. There is no additional brake control requiredSONY VGP-BPS13A/Q Battery .

Synchronous electric motor

A synchronous electric motor is an AC motor distinguished by a rotor spinning with coils passing magnets at the same rate as the alternating current and resulting magnetic field which drives it   SONY VGP-BPS13B/Q Battery .

Another way of saying this is that it has zero slip under usual operating conditions. Contrast this with an induction motor, which must slip to produce torque. A synchronous motor is like an induction motor except the rotor is excited by a DC field. Slip rings and brushes are used to conduct current to rotor   SONY VGP-BPS13B/Q Battery .

The rotor poles connect to each other and move at the same speed hence the name synchronous motor.

Induction motor

An induction motor is an asynchronous AC motor where power is transferred to the rotor by electromagnetic induction  SONY VGP-BPS13/Q Battery .

An induction motor resembles a rotating transformer, because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Polyphase induction motors are widely used in industry  SONY VGP-BPS13/Q Battery .

Induction motors may be further divided into squirrel-cage motors and wound-rotor motors. Squirrel-cage motors have a heavy winding made up of solid bars, usually aluminum or copper, joined by rings at the ends of the rotor. Currents induced into this winding provide the rotor magnetic field        SONY VGP-BPS21A/B Battery .

The shape of the rotor bars determines the speed-torque characteristics. At low speeds, the current induced in the squirrel cage is nearly at line frequency and tends to flow in the outer parts of the rotor cage. As the motor accelerates, the slip frequency becomes lower, and more current flows in the interior of the winding   SONY VGP-BPS21/S Battery .

By shaping the bars to change the resistance of the windings portions in the interior and outer parts of the cage, effectively a variable resistance is inserted in the rotor circuit.

In a wound-rotor motor, the rotor winding is made of many turns of insulated wire and is connected to slip rings on the motor shaft. An external resistor or other control devices can be connected in the rotor circuit  SONY VGP-BPS21B Battery .

Resistors allow control of the motor speed, although significant power is dissipated in the external resistance. A converter can be fed from the rotor circuit and return the slip-frequency power that would otherwise be wasted back into the power system  SONY VGP-BPS21A Battery .

The wound-rotor induction motor is used primarily to start a high inertia load or a load that requires a very high starting torque across the full speed range. By correctly selecting the resistors used in the secondary resistance or slip ring starter, the motor is able to produce maximum torque at a relatively low supply current from zero speed to full speed  SONY VGP-BPS21 Battery .

This type of motor also offers controllable speed.

Motor speed can be changed because the torque curve of the motor is effectively modified by the amount of resistance connected to the rotor circuit. Increasing the value of resistance will move the speed of maximum torque down  Sony VGP-BPS21A/B Battery .

If the resistance connected to the rotor is increased beyond the point where the maximum torque occurs at zero speed, the torque will be further reduced.

When used with a load that has a torque curve that increases with speed, the motor will operate at the speed where the torque developed by the motor is equal to the load torque  Sony VGP-BPS21/S Battery .

Reducing the load will cause the motor to speed up, and increasing the load will cause the motor to slow down until the load and motor torque are equal. Operated in this manner, the slip losses are dissipated in the secondary resistors and can be very significant. The speed regulation and net efficiency is also very poor  Sony VGP-BPS21A Battery .

Doubly-fed electric motor

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. The talk page may contain suggestions. (February 2011)  Sony VGP-BPS21 Battery .

Doubly-fed electric motors have two independent multiphase winding set, which contribute active (i.e., working) power to the energy conversion process, with at least one of the winding sets electronically controlled for variable speed operation  Sony Vaio PCG-5G2L Battery .

Two independent multiphase winding sets (i.e., dual armature) are the maximum provided in a single package without topology duplication. Doubly-fed electric motors are machines with an effective constant torque speed range that is twice synchronous speed for a given frequency of excitation   Sony Vaio PCG-5G3L Battery .

This is twice the constant torque speed range as singly-fed electric machines, which have only one active winding set.

A doubly-fed motor allows for a smaller electronic converter but the cost of the rotor winding and slip rings may offset the saving in the power electronics components. Difficulties with controlling speed near synchronous speed limit applications  Sony Vaio PCG-5J1L Battery .

Singly-fed electric motor

Most AC motors are singly-fed. Singly-fed electric motors have a single multiphase winding set that is connected to a power supply. Singly-fed electric machines may be either induction or synchronous  Sony Vaio PCG-5K2L Battery .

The active winding set can be electronically controlled. Singly-fed electric machines have an effective constant torque speed range up to synchronous speed for a given excitation frequency.

Servo motor

A servomotor is used within a position-control or speed-control feedback control system  Sony Vaio PCG-5J2L Battery .

Servomotors are used in applications such as machine tools, pen plotters, and other control systems. Motors intended for use in a servomechanism must have well-documented characteristics for speed, torque, power. The dynamic response characteristics such as winding inductance and rotor inertia are also important   Sony Vaio PCG-5K1L Battery ;

these factors limit the overall performance of the servomechanism loop. Large, powerful, but slow-responding servo loops may use conventional AC or DC motors and drive systems with position or speed feedback on the motor. As dynamic response requirements increase, more specialized motor designs such as coreless motors are used  Sony Vaio PCG-6S2L Battery .

A servo system differs from some stepper motor applications in that the position feedback is continuous while the motor is running; a stepper system relies on the motor not to "miss steps" for short term accuracy, although a stepper system may include a "home" switch or other element to provide long-term stability of control  Sony Vaio PCG-6S3L Battery .

Electrostatic motor

An electrostatic motor is based on the attraction and repulsion of electric charge. Usually, electrostatic motors are the dual of conventional coil-based motors       Sony Vaio PCG-6V1L Battery .

They typically require a high voltage power supply, although very small motors employ lower voltages. Conventional electric motors instead employ magnetic attraction and repulsion, and require high current at low voltages. In the 1750s, the first electrostatic motors were developed by Benjamin Franklin and Andrew Gordon  Sony Vaio PCG-6W1L Battery .

Today the electrostatic motor finds frequent use in micro-mechanical (MEMS) systems where their drive voltages are below 100 volts, and where moving, charged plates are far easier to fabricate than coils and iron cores. Also, the molecular machinery which runs living cells is often based on linear and rotary electrostatic motors  Sony Vaio PCG-6W2L Battery .

Torque motors

A torque motor (also known as a limited torque motor) is a specialized form of induction motor which is capable of operating indefinitely while stalled, that is, with the rotor blocked from turning, without incurring damage  Sony Vaio PCG-6W3L Battery .

In this mode of operation, the motor will apply a steady torque to the load (hence the name).

A common application of a torque motor would be the supply- and take-up reel motors in a tape drive  Sony Vaio PCG-7111L Battery.

In this application, driven from a low voltage, the characteristics of these motors allow a relatively constant light tension to be applied to the tape whether or not the capstan is feeding tape past the tape heads. Driven from a higher voltage, (and so delivering a higher torque)       Sony Vaio PCG-7112L Battery .

the torque motors can also achieve fast-forward and rewind operation without requiring any additional mechanics such as gears or clutches. In the computer gaming world, torque motors are used in force feedback steering wheels   Sony Vaio PCG-7113L Battery .

Another common application is the control of the throttle of an internal combustion engine in conjunction with an electronic governor. In this usage, the motor works against a return spring to move the throttle in accordance with the output of the governorSony Vaio PCG-7133L Battery .

The latter monitors engine speed by counting electrical pulses from the ignition system or from a magnetic pickup and, depending on the speed, makes small adjustments to the amount of current applied to the motor. If the engine starts to slow down relative to the desired speed      Sony Vaio PCG-7Z2L Battery ,

the current will be increased, the motor will develop more torque, pulling against the return spring and opening the throttle. Should the engine run too fast, the governor will reduce the current being applied to the motor, causing the return spring to pull back and close the throttle  Sony Vaio PCG-8Y1L Battery .

Stepper motors

Closely related in design to three-phase AC synchronous motors are stepper motors, where an internal rotor containing permanent magnets or a magnetically soft rotor with salient poles is controlled by a set of external magnets that are switched electronicallySony Vaio PCG-8Y2L Battery .

A stepper motor may also be thought of as a cross between a DC electric motor and a rotary solenoid. As each coil is energized in turn, the rotor aligns itself with the magnetic field produced by the energized field winding. Unlike a synchronous motor, in its application, the stepper motor may not rotate continuously  Sony Vaio PCG-8Z1L Battery ;

instead, it "steps" — starts and then quickly stops again — from one position to the next as field windings are energized and de-energized in sequence. Depending on the sequence, the rotor may turn forwards or backwards, and it may change direction, stop, speed up or slow down arbitrarily at any time  Sony Vaio PCG-8Z2L Battery .

Simple stepper motor drivers entirely energize or entirely de-energize the field windings, leading the rotor to "cog" to a limited number of positions; more sophisticated drivers can proportionally control the power to the field windings, allowing the rotors to position between the cog points and thereby rotate extremely smoothly  SONY VAIO VGN-FW31J Battery .

This mode of operation is often called microstepping. Computer controlled stepper motors are one of the most versatile forms of positioning systems, particularly when part of a digital servo-controlled system.

Stepper motors can be rotated to a specific angle in discrete steps with ease, and hence stepper motors are used for read/write head positioning in computer floppy diskette drives       SONY VAIO VGN-FW31E Battery .

They were used for the same purpose in pre-gigabyte era computer disk drives, where the precision and speed they offered was adequate for the correct positioning of the read/write head of a hard disk drive. As drive density increased, the precision and speed limitations of stepper motors made them obsolete for hard drives SONY VAIO VGN-FW31B Battery —

the precision limitation made them unusable, and the speed limitation made them uncompetitive—thus newer hard disk drives use voice coil-based head actuator systems. (The term "voice coil" in this connection is historic; it refers to the structure in a typical (cone type) loudspeaker       SONY VAIO VGN-FW31M Battery .

This structure was used for a while to position the heads. Modern drives have a pivoted coil mount; the coil swings back and forth, something like a blade of a rotating fan. Nevertheless, like a voice coil, modern actuator coil conductors (the magnet wire) move perpendicular to the magnetic lines of force     SONY VAIO VGN-FW31Z Battery .)

Stepper motors were and still are often used in computer printers, optical scanners, and digital photocopiers to move the optical scanning element, the print head carriage (of dot matrix and inkjet printers), and the platen        SONY VAIO VGN-FW38M Battery .

Likewise, many computer plotters (which since the early 1990s have been replaced with large-format inkjet and laser printers) used rotary stepper motors for pen and platen movement; the typical alternatives here were either linear stepper motors or servomotors with complex closed-loop control systems  SONY VAIO VGN-AW41JF Battery .

So-called quartz analog wristwatches contain the smallest commonplace stepping motors; they have one coil, draw very little power, and have a permanent-magnet rotor. The same kind of motor drives battery-powered quartz clocks. Some of these watches, such as chronographs, contain more than one stepping motor  SONY VAIO VGN-AW41JF/H Battery .

Stepper motors were upscaled to be used in electric vehicles under the term SRM (Switched Reluctance Motor).

Linear motors

A linear motor is essentially an electric motor that has been "unrolled" so that, instead of producing a torque (rotation), it produces a straight-line force along its length by setting up a traveling electromagnetic field   SONY VAIO VGN-AW41MF Battery .

Linear motors are most commonly induction motors or stepper motors. You can find a linear motor in a maglev (Transrapid) train, where the train "flies" over the ground, and in many roller-coasters where the rapid motion of the motorless railcar is controlled by the rail     SONY VAIO VGN-AW41MF/H Battery .

On a smaller scale, at least one letter-size (8.5" x 11") computer graphics X-Y pen plotter made by Hewlett-Packard (in the late 1970s to mid 1980's) used two linear stepper motors to move the pen along the two orthogonal axes.

Nanotube nanomotor

Researchers at University of California, Berkeley, recently developed rotational bearings based upon multiwall carbon nanotubesSONY VAIO VGN-AW41XH Battery .

By attaching a gold plate (with dimensions of the order of 100 nm) to the outer shell of a suspended multiwall carbon nanotube (like nested carbon cylinders), they are able to electrostatically rotate the outer shell relative to the inner core. These bearings are very robust; devices have been oscillated thousands of times with no indication of wear  SONY VAIO VGN-AW41XH/Q Battery .

These nanoelectromechanical systems (NEMS) are the next step in miniaturization and may find their way into commercial applications in the future  SONY VAIO VGN-AW41ZF Battery .

Spacecraft propulsive motors

An electrically powered spacecraft propulsion system is any of a number of forms of electric motors which spacecraft can employ to gain mechanical energy in outer space   SONY VAIO VGN-AW41ZF/B Battery .

Most of these kinds of spacecraft propulsion work by electrically powering propellant to high speed, but electrodynamic tethers work by interacting with a planet's magnetosphere      SONY VAIO VGN-AW450DB/H Battery .

Energy conversion by an electric motor

Using mathematical models in terms of a magnetic dipole, Ribari? and Šušterši? consider how in the case of the synchronous motor and induction motor an external source is supplying electrical energy to the stator so as to maintain its revolving magnetic field  SONY VAIO VGN-AW51JGB Battery ;

this energy is then transmitted by the revolving magnetic field to the magnetic dipole of the rotor; there it is converted into mechanical energy, and transmitted mechanically by the rotating shaft to an external user      SONY VAIO VGN-AW52JGB Battery .

On the other hand, in the case of a commutator motor, the external source delivers electrical energy directly to the rotor magnetic dipole for conversion into mechanical energy.


The power output of a rotary electric motor is     SONY VAIO VGN-AW70B/Q Battery ;

Where P is in horsepower, rpm is the shaft speed in revolutions per minute and T is the torque in foot pounds.

And for a linear motor:

Where P is the power in watts, and F is in Newtons and v is the speed in metres per second  SONY VAIO VGN-AW71JB Battery .


To calculate a motor's efficiency, the mechanical output power is divided by the electrical input power:,

where ? is energy conversion efficiency, Pe is electrical input power, and Pm is mechanical output power    SONY VAIO VGN-AW73FB Battery.

In simplest case Pe = VI, and Pm = T?, where V is input voltage, I is input current, T is output torque, and ? is output angular velocity. It is possible to derive analytically the point of maximum efficiency. It is typically at less than 1/2 the stall torque SONY VAIO VGN-AW80NS Battery .

Goodness factor

Professor Eric Laithwaite proposed a metric to determine the 'goodness' of an electric motor:


G is the goodness factor (factors above 1 are likely to be efficient)   SONY VAIO VGN-AW80US Battery

Am,Ae are the cross sections of the magnetic and electric circuit

lm,le are the lengths of the magnetic and electric circuits

? is the permeability of the core          SONY VAIO VGN-AW80S Battery

? is the angular frequency the motor is driven at

From this he showed that the most efficient

motors are likely to be relatively large. However, the equation only directly relates to non permanent magnet motors   SONY VAIO VGN-AW80DS Battery .

Torque capability of motor types

When optimally designed within a given core saturation constraint and for a given active current (i.e., torque current), voltage, pole-pair number, excitation frequency (i.e., synchronous speed), and air-gap flux density  SONY VAIO VGN-AW81JS Battery ,

all categories of electric motors or generators will exhibit virtually the same maximum continuous shaft torque (i.e., operating torque) within a given air-gap area with winding slots and back-iron depth, which determines the physical size of electromagnetic core  SONY VAIO VGN-AW81YS Battery .

Some applications require bursts of torque beyond the maximum operating torque, such as short bursts of torque to accelerate an electric vehicle from standstill. Always limited by magnetic core saturation or safe operating temperature rise and voltage  SONY VAIO VGN-AW82DS Battery ,

the capacity for torque bursts beyond the maximum operating torque differs significantly between categories of electric motors or generators.

Capacity for bursts of torque should not be confused with field weakening capability inherent in fully electromagnetic electric machines (Permanent Magnet (PM) electric machine are excluded)  SONY VAIO VGN-AW82JS Battery .

Field weakening, which is not available with PM electric machines, allows an electric machine to operate beyond the designed frequency of excitation.

Electric machines without a transformer circuit topology        SONY VAIO VGN-AW82YS Battery ,

such as Field-Wound (i.e., electromagnet) or Permanent Magnet (PM) Synchronous electric machines cannot realize bursts of torque higher than the maximum designed torque without saturating the magnetic core and rendering any increase in current as useless  SONY VAIO VGN-AW83FS Battery .

Furthermore, the permanent magnet assembly of PM synchronous electric machines can be irreparably damaged, if bursts of torque exceeding the maximum operating torque rating are attempted.

Electric machines with a transformer circuit topology, such as Induction (i.e., asynchronous) electric machines  SONY VAIO VGN-AW83GS Battery ,

Induction Doubly-Fed electric machines, and Induction or Synchronous Wound-Rotor Doubly-Fed (WRDF) electric machines, exhibit very high bursts of torque because the active current (i.e., Magneto-Motive-Force or the product of current and winding-turns) induced on either side of the transformer oppose each other and as a result  SONY VAIO VGN-AW83HS Battery ,

the active current contributes nothing to the transformer coupled magnetic core flux density, which would otherwise lead to core saturation.

Electric machines that rely on Induction or Asynchronous principles short-circuit one port of the transformer circuit and as a resultSONY VAIO VGN-AW90NS Battery ,

the reactive impedance of the transformer circuit becomes dominant as slip increases, which limits the magnitude of active (i.e., real) current. Still, bursts of torque that are two to three times higher than the maximum design torque are realizable  SONY VAIO VGN-AW90S Battery .

The Synchronous WRDF electric machine is the only electric machine with a truly dual ported transformer circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate limited power to the rotor winding set  SONY VAIO VGN-AW90US Battery .

If a precision means were available to instantaneously control torque angle and slip for synchronous operation during motoring or generating while simultaneously providing brushless power to the rotor winding set (see Brushless wound-rotor doubly-fed electric machine)     SONY VAIO VGN-AW91CDS Battery ,

the active current of the Synchronous WRDF electric machine would be independent of the reactive impedance of the transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond the practical capability of any other type of electric machine would be realizable  SONY VAIO VGN-AW91CJS Battery .

Torque bursts greater than eight times operating torque have been calculated.

Continuous Torque Density

The continuous torque density of conventional electric machines is determined by the size of the air-gap area and the back-iron depth   SONY VAIO VGN-AW91CYS Battery .

which are determined by the power rating of the armature winding set, the speed of the machine, and the achievable air-gap flux density before core saturation. Despite the high coercivity of neodymium or samarium-cobalt permanent magnets, continuous torque density is virtually the same amongst electric machines with optimally designed armature winding sets SONY VAIO VGN-AW91JS Battery .

Continuous torque density should never be confused with peak torque density, which comes with the manufacturer's chosen method of cooling, which is available to all, or period of operation before destruction by overheating of windings or even permanent magnet damage SONY VAIO VGN-AW91YS Battery .

Continuous Power Density

The continuous power density is determined by the product of the continuous torque density and the constant torque speed range of the electric machine  SONY VAIO VGN-AW92CDS Battery .

Motor standards

The following are major design and manufacturing standards covering electric motors:

International Electrotechnical Commission: IEC 60034 Rotating Electrical Machines  SONY VAIO VGN-AW92CJS Battery

National Electrical Manufacturers Association (USA): NEMA MG 1 Motors and Generators

Underwriters Laboratories (USA): UL 1004 - Standard for Electric Motors   SONY VAIO VGN-AW92CYS Battery


Electric motors are used in many, if not most, modern machines. Obvious uses would be in rotating machines such as fans, turbines, drills, the wheels on electric cars, locomotives and conveyor belts   SONY VAIO VGN-AW92DS Battery .

Also, in many vibrating or oscillating machines, an electric motor spins an irregular figure with more area on one side of the axle than the other, causing it to appear to be moving up and down.

Electric motors are also popular in robotics   SONY VAIO VGN-AW92JS Battery .

They are used to turn the wheels of vehicular robots, and servo motors are used to turn arms and legs in humanoid robots. In flying robots, along with helicopters, a motor causes a propeller or wide, flat blades to spin and create lift force, allowing vertical motion.

Electric motors are replacing hydraulic cylinders in airplanes and military equipment   SONY VAIO VGN-AW92YS Battery .

In industrial and manufacturing businesses, electric motors are used to turn saws and blades in cutting and slicing processes, and to spin gears and mixers (the latter very common in food manufacturing). Linear motors are often used to push products into containers horizontally   SONY VAIO VGN-AW93FS Battery .

Many kitchen appliances also use electric motors. Food processors and grinders spin blades to chop and break up foods. Blenders use electric motors to mix liquids, and microwave ovens use motors to turn the tray food sits on. Toaster ovens also use electric motors to turn a conveyor to move food over heating elements  SONY VAIO VGN-BZ31XT Battery .

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The IEEE 1394 interface is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used bypersonal computers, as well as in digital audio, digital video, automotive, and aeronautics applications    (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

The interface is also known by the brand names ofFireWire (Apple), i.LINK (Sony), and Lynx (Texas Instruments). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementationcosts and a simplified, more adaptable cabling system. The 1394 standard also defines a backplane interface, though this is not as widely used  Dell Studio XPS 1640 Battery .

IEEE 1394 is the High-Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control. FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols  Dell Vostro 1710 Battery .

Nearly all digital camcorders have included a four-circuit 1394 interface, though, except for premium models, such inclusion is becoming less common. It remains the primary transfer mechanism for high-end professional audio and video equipment  Dell KM958 battery .

Since 2003, many computers intended for home or professional audio/video use have built-in FireWire/i.LINK ports, especially prevalent with Sony and Apple's computers. The legacy (alpha) 1394 port is also available on premium retail motherboards Dell Studio 1555 battery .

History and development

FireWire is Apple's name for the IEEE 1394 High Speed Serial Bus. It was initiated by Apple (in 1986[2]) and developed by the IEEE P1394 Working Group, largely driven by contributions from Apple, although major contributions were also made by engineers from Texas Instruments, Sony, Digital Equipment Corporation, IBM, and INMOS/SGS Thomson (now STMicroelectronics)   Sony VGP-BPS13 battery .

IEEE 1394 is a serial bus architecture for high-speed data transfer. Compared to older avionics data buses such as MIL-STD-1553, FireWire is a serial bus, meaning that information is transferred one bit at a time. Parallel buses utilize a number of different physical connections, and as such are usually much less efficient, more costly, and typically heavier   Sony VGP-BPS13/B battery .

Unlike other serial buses, such as PCI, FireWire fully supports both isochronous and asynchronous applications such as in safety-critical systems in the F-22 Raptor.

Apple intended FireWire to be a serial replacement for the parallel SCSI bus while providing connectivity for digital audio and video equipment   Sony VGP-BPS13/S battery .

Apple's development began in the late 1980s, later presented to the IEEE,  and was completed in 1995. As of 2007, IEEE 1394 is a composite of four documents: the original IEEE Std. 1394-1995, the IEEE Std. 1394a-2000 amendment, the IEEE Std. 1394b-2002 amendment, and the IEEE Std. 1394c-2006 amendment   Sony VGP-BPS13A/B battery .

On June 12, 2008, all these amendments as well as errata and some technical updates were incorporated into a superseding standard IEEE Std. 1394-2008.

Apple's internal long-time code-name for FireWire was "Chefcat" starting in 1988 as the team sat around a conference table contemplating what to call the project and staring at Michael Johas Teener's famous Kliban coffee mug  Sony VGP-BPS13B/B battery .

That was the "aha" moment articulating the goals of the new interconnect, at low cost and ultimate simplicity presented to the user to replace and unify all other PC interconnections and expand beyond that base to enable ultimate miniaturization of electronics  Sony VGP-BPL9 battery .

The concept of the current loop electronics that became the now pervasive LVDS was code named "Greyhound" around 1992.

Sony's implementation of the system, "i.LINK", used a smaller connector with only the four signal circuits, omitting the two circuits which provide power to the device in favor of a separate power connector  Sony VGP-BPS13B/B battery .

This style was later added into the 1394a amendment.This port is sometimes labeled "S100" or "S400" to indicate speed in Mbit/s.

The system is commonly used for connection of data storage devices and DV (digital video) cameras, but is also popular in industrial systems for machine vision and professional audio systems   Sony VGP-BPL15 battery .

It is preferred over the more common USB for its greater effective speed and power distribution capabilities. Perhaps more important, FireWire uses all SCSI capabilities and has high sustained data transfer rates, important for audio and video editors  Dell Inspiron E1505 battery .

Benchmarks show that the sustained data transfer rates are higher for FireWire than for USB 2.0, but lower than USB 3.0. Results are marked on Apple Mac OS X but more varied on Microsoft Windows.

However, the expensive hardware needed to implement it (US$1–$2) has prevented FireWire from displacing USB in low-end mass-market computer peripherals, where product cost is a major constraint  Dell Latitude E6400 battery .

Under the license offered by MPEG LA, a royalty of US$0.25 per unit is payable upon the manufacture of each 1394 product.

Technical specifications

FireWire can connect up to 63 peripherals in a tree chain topology (as opposed to Parallel SCSI's electrical bus topology)  HP Pavilion dv6000 Battery .

It allows peer-to-peer device communication — such as communication between a scanner and a printer — to take place without using system memory or the CPU. FireWire also supports multiple hosts per bus. It is designed to support plug and play but not hot swapping  SONY VAIO VGN-FZ Battery .

The copper cable it uses (1394's most common implementation) can be up to 4.5 metres (15 ft) long and is more flexible than most Parallel SCSI cables. In its six-circuit or nine-circuit variations, it can supply up to 45 watts of power per port at up to 30 volts, allowing moderate-consumption devices to operate without a separate power supply  SONY VAIO VGN-FZ18 Battery .

FireWire devices implement the ISO/IEC 13213 "configuration ROM" model for device configuration and identification, to provide plug-and-play capability. All FireWire devices are identified by an IEEE EUI-64 unique identifier (an extension of the 48-bit Ethernet MAC address format) in addition to well-known codes indicating the type of device and the protocols it supports  SONY VAIO VGN-FZ21E Battery .

FireWire devices are organized at the bus in a tree topology. Each device has a unique self-id. One of the nodes is elected root node and always has the highest id. The self-ids are assigned during the self-id process, which happens after each bus resets  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

The order in which the self-ids are assigned is equivalent to traversing the tree depth-first, post-order.

FireWire is capable of operating safety critical systems due to the way multiple devices interact with the bus and how the bus allocates bandwidth to the devices  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

FireWire is capable of both asynchronous and isochronous transfer methods at once. Isochronous data transfers are transfers for devices that require continuous, guaranteed bandwidth. Isochronous devices include control of the rudder, mouse operations and data from pressure sensors outside the aircraft       SONY VAIO VGN-FW21E Battery .

All these elements require constant, uninterrupted bandwidth. Asynchronous data transfers are for devices which use a buffer, such as streaming video, speakers and CD drives. To support both elements, FireWire dedicates a certain percentage to isochronous data and the rest to asynchronous data    SONY VAIO VGN-NR11S/S Battery .

In IEEE 1394 80% of the bus is reserved for isochronous cycles, leaving asynchronous data with a minimum of 20% of the bus.

Encoding Scheme

FireWire uses Data strobe encoding (D/S encoding).  In D/S encoding, two non-return-to-zero (NRZ) signals are used to transmit the data with high reliability         SONY VAIO VGN-NR11M/S Battery .

The NRZ signal sent is fed with the clock signal through an XOR gate, creating a strobe signal. This strobe is then put through another XOR gate along with the data signal to reconstruct the clock.This in turn acts as the bus's PLL for synchronization purposes  SONY VAIO VGN-NR11Z/S Battery .


The process of the bus deciding which node gets to transmit data at what time is known as arbitration. Each arbitration round lasts about 125 micro-seconds. During the round, the root node (device nearest the processor) sends a cycle start packet. All nodes requiring data transfer respond, with the closest node winning  SONY VAIO VGN-NR11Z/T Battery .

After the node is finished, the remaining nodes take turns in order. This repeats until all the devices have used their portion of the 125 micro-seconds, with isochronous transfers having priority. Up to 80% of the time can be given to isochronous nodes  Sony VAIO VGN-FZ21E Battery .

Standards and versions

The previous standards and its three published amendments are now incorporated into a superseding standard, IEEE 1394-2008.The features individually added give a good history on the development path  Sony VAIO VGN-FW21E Battery .

FireWire 400 (IEEE 1394-1995)

The original release of IEEE 1394-1995  specified what is now known as FireWire 400. It can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates (the actual transfer rates are 98.304, 196.608, and 393.216 Mbit/s, i.e., 12.288, 24.576 and 49.152 megabytes per second respectively)  Sony VAIO VGN-NR11S/S Battery .

These different transfer modes are commonly referred to as S100, S200, and S400.

Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chained using active repeaters; external hubs, or internal hubs are often present in FireWire equipment     Sony VAIO VGN-NR11Z/S Battery .

The S400 standard limits any configuration's maximum cable length to 72 metres (236 ft). The 6-circuit connector is commonly found on desktop computers, and can supply the connected device with power.

The 6-circuit powered connector, now referred to as an alpha connector, adds power output to support external devices  Sony VAIO VGN-NR11M/S Battery .

Typically a device can pull about 7 to 8 watts from the port; however, the voltage varies significantly from different devices. Voltage is specified as unregulated and should nominally be about 25 volts (range 24 to 30). Apple's implementation on laptops is typically related to battery power and can be as low as 9 V     Sony VAIO VGN-NR11Z/T Battery .

Improvements (IEEE 1394a-2000)

An amendment, IEEE 1394a, was released in 2000,  which clarified and improved the original specification. It added support for asynchronous streaming, quicker bus reconfiguration, packet concatenation, and a power-saving suspend mode  SONY VAIO VGN-FZ180E Battery .

IEEE 1394a offers a couple of advantages over IEEE 1394. 1394a is capable of arbitration accelerations, allowing the bus to accelerate arbitration cycles to improve efficiency. It also allows for arbitrated short bus reset, in which a node can be added or dropped without causing a big drop in isochronous transmission  SONY VAIO VGN-FZ220E Battery .

1394a also standardized the 4-circuit alpha connector developed by Sony and trademarked as "i.LINK", already widely in use on consumer devices such as camcorders, most PC laptops, a number of PC desktops, and other small FireWire devices. The 4-circuit connector is fully data-compatible with 6-circuit alpha interfaces but lacks power connectors SONY VAIO VGN-FZ340E Battery .

FireWire 800 (IEEE 1394b-2002)


IEEE 1394b-2002  introduced FireWire 800 (Apple's name for the 9-circuit "S800 bilingual" version of the IEEE 1394b standard) This specification and corresponding products allow a transfer rate of 786.432 Mbit/s full-duplex via a new encoding scheme termed beta mode  SONY VAIO VGN-FZ430E Battery .

It is backwards compatible to the slower rates and 6-circuit alpha connectors of FireWire 400. However, while the IEEE 1394a and IEEE 1394b standards are compatible, FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible  SONY VAIO VGN-FZ460E Battery .

A bilingual cable allows the connection of older devices to the newer port. In 2003, Apple was the first to introduce commercial products with the new connector.

The full IEEE 1394b specification supports data rates up to 3200 Mbit/s (i.e., 400 megabytes/s) over beta-mode or optical connections up to 100 metres (330 ft) in length. Standard Category 5e unshielded twisted pair supports 100 metres (330 ft) at S100SONY VAIO VGN-FZ480E Battery .

The original 1394 and 1394a standards used data/strobe (D/S) encoding (renamed to alpha mode) on the circuits, while 1394b adds a data encoding scheme called 8B10B referred to as beta mode  SONY VAIO VGN-FZ4000 Battery .

Beta mode is based on 8B/10B (Gigabit Ethernet & Fibre Channel). 8B/10B encoding involves expanding an 8 bit data word into 10 bits, with the extra bits after the 5th and 8th data bits. The partitioned data is sent through a Running Disparity calculator function  SONY VAIO VGN-FZ31E Battery .

The Running Disparity calculator attempts to keep the number of 1s transmitted equal to 0s, thereby assuring a DC-balanced signal. Then, the different partitions are sent through a 5B/6B encoder for the 5 bit partition and a 3B/4B encoder for the 3 bit partitionSONY VAIO VGN-FZ31B Battery .

This gives the packet the ability to have at least two 1s, ensuring synchronization of the PLL at the receiving end to the correct bit boundaries for reliable transfer. An additional function of the coding scheme is to support the arbitration for bus access and general bus control     SONY VAIO VGN-FZ31J Battery .

This is possible due to the "surplus" symbols afforded by the 8B/10B expansion. (While 8-bit symbols can encode a maximum of 256 values, 10-bit symbols permit the encoding of up to 1024.) Symbols invalid for the current state of the receiving PHY indicate data errors   SONY VAIO VGN-FZ31M Battery .

FireWire S1600 and S3200

In December 2007, the 1394 Trade Association announced that products would be available before the end of 2008 using the S1600 and S3200 modes that, for the most part, had already been defined in 1394b and was further clarified in IEEE Std. 1394-2008 SONY VAIO VGN-FZ31Z Battery .

The 1.6 Gbit/s and 3.2 Gbit/s devices use the same 9-circuit beta connectors as the existing FireWire 800 and will be fully compatible with existing S400 and S800 devices. It will compete with the forthcoming USB 3.0.

S1600 (Symwave  ) and S3200 (Dap Technology ) development units have been made, with the latter promising a consumer version by late 2010  SONY VAIO VGN-FZ38M Battery .

FireWire S800T (IEEE 1394c-2006)

It provided a major technical improvement, namely new port specification that provides 800 Mbit/s over the same 8P8C (Ethernet) connectors with Category 5e cable       SONY VGP-BPS8 Battery ,

which is specified in IEEE 802.3 clause 40 (gigabit Ethernet over copper twisted pair) along with a corresponding automatic negotiation that allows the same port to connect to either IEEE Std 1394 or IEEE 802.3 (Ethernet) devices  SONY VGP-BPS13/S Battery .

Though the potential for a combined Ethernet and FireWire 8P8C port is intriguing, as of November 2008, there are no products or chipsets which include this capability.

Future enhancements (including P1394d)

A project named IEEE P1394d was formed by the IEEE on March 9, 2009 to add single mode fiber as an additional transport medium to FireWire    SONY VGP-BPS13A/B Battery .

Other future iterations of FireWire are expected to bring a bump in speed to 6.4 Gbit/s and additional connectors such as the small multimedia interface.

Operating system support

Full support for IEEE 1394a and 1394b is available for Microsoft Windows, FreeBSD,  Linux, Apple Mac OS 8.6 through Mac OS 9, Mac OS X, NetBSD, and Haiku  SONY VGP-BPS13B/B Battery .

In Windows XP, a degradation in performance of 1394 devices may have occurred with installation of Service Pack 2. This was resolved in Hotfix 885222 and in SP3. Some FireWire hardware manufacturers also provide custom device drivers which replace the Microsoft OHCI host adapter driver stack  SONY VGP-BPS13A/S Battery ,

enabling S800-capable devices to run at full 800 Mbit/s transfer rates on older versions of Windows (XP SP2 w/o Hotfix 885222) and Windows Vista. At the time of its release, Microsoft Windows Vista supported only 1394a, with assurances that 1394b support would come in the next service pack  SONY VGP-BPS13AS Battery .

Service Pack 1 for Microsoft Windows Vista has since been released, however the addition of 1394b support is not mentioned anywhere in the release documentation. The 1394 bus driver was rewritten for Windows 7 to provide support for higher speeds and alternative media  Dell Inspiron 1320n Battery .

In Linux, support was originally provided by libraw1394 making direct communication between user space and IEEE 1394 buses. Subsequently a new kernel driver stack, nicknamed JuJu, has been implemented.

Cable TV system support

Cable TV providers (in the US, with digital systems) must, upon request of a customer, provide a high-definition capable cable box with a functional FireWire interface  Dell Inspiron 1464 Battery .

This applies only to customers leasing high-definition capable cable boxes from said cable provider after April 1, 2004. The relevant law is 47 CFR 76.640 Section 4 Subsections i and ii. The interface can be used to display or record Cable TV, including HDTV programming    Dell Inspiron 1564 Battery .

Comparison with USB

While USB 2.0 (introduced in 2001) is quoted as running at a higher signaling rate (480 Mbit/s) than legacy FireWire 400 (400 Mbit/s, available since 1995), data transfers over S400 FireWire interfaces generally outperform similar transfers over USB 2.0 interfaces in real world environments    Dell Inspiron 1764 Battery .

Few if any USB 2.0 device implementations are capable of saturating the entire 480 Mbit/s, but this can be achieved with multiple devices on the same bus. In real world tests USB PC hosts rarely can sustain transfers exceeding 280 Mbit/s, with 240 Mbit/s being the norm  Dell Studio 1450 Battery .

This is likely due to USB's reliance on the host processor to manage low-level USB protocol, whereas FireWire delegates the same tasks to the interface hardware (requiring less or no CPU usage). For example, the FireWire host interface supports memory-mapped devices, allowing high-level protocols to run without loading the host CPU with interrupts and buffer-copy operations  Dell Studio 1457 Battery .

Other differences are that FireWire uses simpler bus networking, provides more power over the chain and more reliable data transfer, and is less taxing on a CPU. USB requires the presence of a bus master, typically a PC, whereas FireWire is a true peer-to-peer network, thus allowing either device to serve as the host or the slave  Dell Latitude D610 Battery .


IDB-1394 Customer Convenience Port (CCP) is the automotive version of the 1394 standard.

Wind power turbines

Audio monitoring for vibrations in the power transmission in wind driven electrical turbines uses a 1394 network for data gatheringToshiba NB100 Battery .

Networking over FireWire

FireWire can be used for ad-hoc (terminals only, no routers except where a FireWire hub is used) computer networks. Specifically, RFC 2734 specifies how to run IPv4 over the FireWire interface, and RFC 3146 specifies how to run IPv6  Toshiba Satellite M65 battery .

Mac OS X, Linux, and FreeBSD include support for networking over FireWire . Windows Me, Windows XP and Windows Server 2003 include native support for IEEE 1394 networking. Windows 2000 does not have native support but may work with third party drivers  Toshiba Satellite M60 battery .

A network can be set up between two computers using a single standard FireWire cable, or by multiple computers through use of a hub. This is similar to Ethernet networks with the major differences being transfer speed, circuit length, and the fact that standard FireWire cables can be used for point-to-point communication  Dell Latitude D830 Battery .

On December 4, 2004, Microsoft announced that it would discontinue support for IP networking over the FireWire interface in all future versions of Microsoft Windows. Consequently, support for this feature is absent from Windows Vista and later Windows releases  Dell Latitude D620 Battery .

Microsoft rewrote their 1394 driver in Windows 7   but networking support for FireWire is not present. Unibrain offers free FireWire networking drivers for Windows called ubCore  which support Windows Vista and later versions  Dell Inspiron Mini 10 Battery .

The PlayStation 2 console had an i.LINK-branded 1394 connector. This was used for networking until the release of an Ethernet adapter late in the console's lifespan, but very few software titles supported the feature  Sony VGN-FW11S Battery .


IIDC (Instrumentation & Industrial Digital Camera) is the FireWire data format standard for live video, and is used by Apple's iSight A/V camera. The system was designed for machine vision systems but is also used for other computer vision applications and for some webcams  Sony VGN-FW11M Battery .

Although they are easily confused since they both run over FireWire, IIDC is different from, and incompatible with, the ubiquitous AV/C (Audio Video Control) used to control camcorders and other consumer video devices  Sony VGN-FW139E/H battery .


Digital Video (DV) is a standard protocol used by some digital camcorders. All DV cameras that recorded to tape media had a FireWire interface (usually a 4-circuit)  Dell Latitude E5400 Battery .

Labeling of the port varies by manufacturer, with Sony using either its i.LINK trademark or the letters 'DV'. Many digital video recorders have a "DV-input" FireWire connector (usually an alpha connector) which can be used to record video from a directly-connected DV camcorder ("computer-free")  Dell Latitude E4200 Battery .

The protocol also allows remote control (play, rewind, etc.) of connected devices.

It was not possible to use a USB interface for tape based systems because the video was streamed from the tape at a constant rate. USB relied on processor support and this was not guaranteed to service the USB port in time  Dell Inspiron 300M Battery .

The recent move away from tape towards solid state memory or disc media (e.g. SD Cards, DVD disc or Hard Drives), has enabled a switch to USB.

Frame grabbers

IEEE 1394 interface is commonly found in frame grabbers, devices that capture and digitize an analog video signal  Dell Vostro A840 Battery ;

however, IEEE 1394 is facing competition from the Gigabit Ethernet interface (citing speed and availability issues).

Security issues

Devices on a FireWire bus can communicate by direct memory access (DMA), where a device can use hardware to map internal memory to FireWire's "Physical Memory Space"   Dell Studio 1737 battery .

The SBP-2 (Serial Bus Protocol 2) used by FireWire disk drives uses this capability to minimize interrupts and buffer copies. In SBP-2, the initiator (controlling device) sends a request by remotely writing a command into a specified area of the target's FireWire address space     Dell Inspiron E1505 battery .

This command usually includes buffer addresses in the initiator's FireWire "Physical Address Space", which the target is supposed to use for moving I/O data to and from the initiator.

On many implementations, particularly those like PCs and Macs using the popular OHCI, the mapping between the FireWire "Physical Memory Space" and device physical memory is done in hardware, without operating system intervention  Dell RM791 battery .

While this enables high-speed and low-latency communication between data sources and sinks without unnecessary copying (such as between a video camera and a software video recording application, or between a disk drive and the application buffers), this can also be a security risk if untrustworthy devices are attached to the bus   Dell XPS M1530 battery .

For this reason, high-security installations will typically either purchase newer machines which map a virtual memory space to the FireWire "Physical Memory Space" (such as a Power Mac G5, or any Sun workstation), disable the OHCI hardware mapping between FireWire and device memory, physically disable the entire FireWire interface, or do not have FireWire  Dell XPS M2010 battery .

This feature can be used to debug a machine whose operating system has crashed, and in some systems for remote-console operations. On FreeBSD, the dcons driver provides both, using gdb as debugger. Under Linux, firescope  and fireproxy exists  Acer Aspire One battery .

The Institute of Electrical and Electronics Engineers or IEEE (read I-Triple-E) is a non-profit professional association dedicated to advancing technological innovation related to electricity. It has more than 395,000 members in more than 160 countries, 45% outside the United States  Toshiba Satellite P10 Battery .

The IEEE is incorporated under the Not-for-Profit Corporation Law of the state of New York, United States. It was formed in 1963 by the merger of theInstitute of Radio Engineers (IRE, founded 1912) and the American Institute of Electrical Engineers (AIEE, founded 1884)  SONY VGN-FZ210CE Battery .

The major interests of the AIEE were wire communications (telegraph and telephony) and light and power systems. The IRE concerned mostly radioengineering, and was formed from two smaller organizations, the Society of Wireless and Telegraph Engineers and the Wireless Institute   Dell Precision M70 Battery .

With the rise ofelectronics in the 1930s, electronics engineers usually became members of the IRE, but the applications of electron tube technology became so extensive that the technical boundaries differentiating the IRE and the AIEE became difficult to distinguish   Toshiba Satellite L305 Battery .

After World War II, the two organizations became increasingly competitive, and in 1961, the leadership of both the IRE and the AIEE resolved to consolidate the two organizations. The two organizations formally merged as the IEEE on January 1, 1963  Toshiba Satellite T4900 Battery .

Notable Presidents of IEEE and its founding organizations include Elihu Thomson (AIEE, 1889–1890), Alexander Graham Bell (AIEE, 1891–1892), Charles Proteus Steinmetz (AIEE, 1901–1902), Lee De Forest (IRE, 1930), Frederick E. Terman (IRE, 1941), William R. Hewlett (IRE, 1954), Ernst Weber (IRE, 1959; IEEE, 1963), and Ivan Getting (IEEE, 1978)  Toshiba PA3399U-2BRS battery .

IEEE's Constitution defines the purposes of the organization as "scientific and educational, directed toward the advancement of the theory and practice ofElectrical, Electronics, Communications and Computer engineering, as well as computer science, the allied branches of engineering and the related arts andsciences  Toshiba Satellite A200 Battery ."

In pursuing these goals, the IEEE serves as a major publisher of scientific journals and a conference organizer. It is also a leading developer of industrial standards (having developed over 900 active industry standards) in a broad range of disciplinesToshiba Satellite 1200 Battery ,

including electric power and energy, biomedical technology and healthcare, information technology, information assurance, telecommunications, consumer electronics, transportation, aerospace, andnanotechnology. IEEE develops and participates in educational activities such as accreditation of electrical engineering programs in institutes of higher learning  Toshiba Satellite M300 Battery .

The IEEE logo is a diamond-shaped design which illustrates the right hand grip rule embedded in Benjamin Franklin's kite, which was created in the 1963 merger.IEEE also sponsors or cosponsors more than 1000 international technical conferences each year  SONY VGP-BPS13A/Q Battery .

IEEE has a dual complementary regional and technical structure - with organizational units based on geography (e.g., for example the IEEE Philadelphia Section, IEEE South Africa Section ) and technical focus (e.g., the IEEE Computer Society)  SONY VGP-BPS13A/Q Battery .

It manages a separate organizational unit (IEEE-USA) which recommends policies and implements programs specifically intended to benefit the members, the profession and the public in the United States.

The IEEE consists of 38 societies, organized around specialized technical fields, with more than 300 local organizations that hold regular meetings  SONY VGP-BPS13B/Q Battery .

The IEEE Standards Association is in charge of the standardization activities of the IEEE.


IEEE produces 30% of the world's literature in the electrical and electronics engineering and computer science fields, publishing well over 100 peer-reviewed journals  SONY VGP-BPS13B/Q Battery .

The content in these journals as well as the content from several hundred annual conferences are available in the IEEE's online digital library.

IEEE publications have received a Green rating the from SHERPA/RoMEO guide for affirming "authors and/or their companies shall have the right to post their IEEE-copyrighted material on their own servers without permission" (IEEE Publication Policy 8.1.9.D )SONY VGP-BPS13/Q Battery .

This open access policy effectively allows authors, at their choice, to make their article openly available. Roughly 1/3 of the IEEE authors take this route.

Like most other standards bodies, IEEE distributes its standards documents for a fee  SONY VGP-BPS13/Q Battery .

Educational opportunities

The IEEE provides learning opportunities within the engineering sciences, research, and technology. The goal of the IEEE education programs is to ensure the growth of skill and knowledge in the electricity-related technical professions and to foster individual commitment to continuing education among IEEE members  SONY VGP-BPS21A/B Battery ,

the engineering and scientific communities, and the general public.

IEEE offers educational opportunities such as IEEE eLearning Library, the Education Partners Program, Standards in Educationand Continuing Education Units (CEUs)  SONY VGP-BPS21/S Battery .

IEEE eLearning Library is a collection of online educational courses designed for self-paced learning. Education Partners, exclusive for IEEE members, offers on-line degree programs, certifications and courses at a 10% discount. The Standards in Education website explains what standards are and the importance of developing and using them   SONY VGP-BPS21B Battery .

The site includes tutorial modules and case illustrations to introduce the history of standards, the basic terminology, their applications and impact on products, as well as news related to standards, book reviews and links to other sites that contain information on standards       SONY VGP-BPS21A Battery .

Currently, twenty-nine states require Professional Development Hours (PDH) to maintain P.E. licensure, encouraging engineers to seek Continuing Education Units (CEUs) for their participation in continuing education programs. CEUs readily translate into Professional Development Hours (PDHs) (1 CEU is equivalent to 10 PDHs)   SONY VGP-BPS21 Battery .

Countries outside the United States, such as South Africa, also require continuing professional development (CPD) credits. In South Africa, the IEEE South Africa Section is a voluntary association of the Engineering Council of South Africa (ECSA), a signatory of Washington Accord   Sony VGP-BPS21A/B Battery .

To maintain registration with ECSA, professional engineers (Pr Eng) must pursue CPD, and now the IEEE, via its local reflection in South Africa, can enable CPD provision. In 2010, it is anticipated that IEEE Expert Now courses will feature in the CPD listing for the IEEE membership in South Africa to derive benefit  Sony VGP-BPS21/S Battery .

IEEE also sponsors a website designed to help young people understand better what engineering means, and how an engineering career can be made part of their future. Students (ages 8–18), parents, and teachers can explore the site to prepare for an engineering career  Sony VGP-BPS21A Battery ,

ask experts engineering-related questions, play interactive games, explore curriculum links, and review lesson plans. This website also allows students to search for accredited engineering degree programs in Canada and the United States; visitors are able to search by state/province/territory, country, degree field, tuition ranges, room and board ranges, size of student body, and location (rural, suburban, or urban)  Sony VGP-BPS21 Battery .

Standards and development process

IEEE is one of the leading standards-making organizations in the world. IEEE performs its standards making and maintaining functions through the IEEE Standards Association (IEEE-SA)  Sony Vaio PCG-5G2L Battery .

EEE standards affect a wide range of industries including: power and energy, biomedical and healthcare, Information Technology (IT), telecommunications, transportation, nanotechnology, information assurance, and many more. In 2005, IEEE had close to 900 active standards, with 500 standards under development   Sony Vaio PCG-5G3L Battery .

One of the more notable IEEE standards is the IEEE 802 LAN/MAN group of standards which includes the IEEE 802.3 Ethernet standard and the IEEE 802.11 Wireless Networking standard.

Membership and member grades

Most IEEE members are electrical engineers and electronics engineers  Sony Vaio PCG-5J1L Battery ,

but the organization's wide scope of interests has attracted engineers in other disciplines (e.g., computer science, mechanicaland civil engineering) as well as biologists, physicists, and mathematicians. An individual can join the IEEE as an student member, professional member, or associate member   Sony Vaio PCG-5K2L Battery .

In order to qualify for membership, the individual must comply with certain academic or professional criteria and abide to the code of ethics and bylaws of the organization. Student memberships are available to those who are enrolled in a accredited institution of higher education as undergrad or graduate students for a reduced fee  Sony Vaio PCG-5J2L Battery .

A professional membership however requires from the individual proof of having been graduated from an higher education institution and received the diploma or engineer. In the case of some countries like the U.S.A. and Canada, a bachelor in electrical, electronics or computer science are almost automatically considered for membership  Sony Vaio PCG-5K1L Battery .

An associate membership is given to an individual whose area of expertise falls outside the scope of the IEEE and/or don't have at the time of enrollment all the requirements for applying for full memberships. Other individuals who don't want to be directly linked to electrical engineering for reasons of having membership on another sister organizations  Sony Vaio PCG-6S2L Battery ,

may choose to be called affiliates before that professional members of the IEEE. Students and Associates have all the privileges of members, except the right to vote and hold certain offices. Upon meeting certain requirements, a member can apply for a Senior Membership  Sony Vaio PCG-6S3L Battery ,

which is the highest recognition a professional member can host for his(her) contributions and advancement to the field of electrical and electronics engineering. Although an application for Senior Member is personal and optional, the applicant must have at least two letters of recommendation from other senior members and rigorously fulfill the requirements of education Sony Vaio PCG-6V1L Battery ,

achievement, remarkable contribution and experience in the field. The Senior Members are a selected group who are entitled to hold specific IEEE officer positions and is the requirement for those who are nominated and elevated to the grade IEEE Fellow, a distinctive honor  Sony Vaio PCG-6W1L Battery .


Through its awards program, the IEEE advances the interests of its members by recognizing their contributions in advancing the fields of interest to IEEE to the benefit of society   Sony Vaio PCG-6W2L Battery .

By this means, the image and prestige of the organization, its members, and the profession are all enhanced. The IEEE Awards Program honors members and other professionals for their service to the society  Sony Vaio PCG-6W3L Battery .

For nearly a century, the IEEE Awards Program has paid tribute to technical professionals whose exceptional achievements and outstanding contributions have made a lasting impact on technology, society and the engineering profession  Sony Vaio PCG-7111L Battery .

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In computing, the Advanced Configuration and Power Interface (ACPI) specification provides an open standard for unified operating system-centric device configuration and power management     (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

ACPI, first released in December 1996, defines platform-independent interfaces for hardware discovery, configuration, power management and monitoring. The specification is central to Operating System-directed configuration and Power Management(OSPM)      Dell Studio XPS 1640 Battery ;

a term used to describe a system implementing ACPI, which therefore removes device management responsibilities from legacy firmware interfaces. The standard was originally developed by Intel, Microsoft, and Toshiba - later joined by HP and Phoenix. - and last (as of 2010) published as "Revision 4.0a", on April 5, 2010   Dell Vostro 1710 Battery .


ACPI aims to consolidate and improve upon existing power and configuration standards for hardware devices. It provides a transition from existing standards to entirely ACPI-compliant hardware, with some ACPI operating systems already removing support for legacy hardware       Dell KM958 battery .

With the intention of replacing Advanced Power Management, the MultiProcessor Specification and the Plug and Play BIOS Specification, the standard brings power management into operating system control (OSPM), as opposed to the previous BIOS central system, which relied on platform-specific firmware to determine power management and configuration policy  Dell Studio 1555 battery .

The ACPI specification contains numerous related components for hardware and software programming, as well as a unified standard for device/power interaction and bus configuration. As a document that unifies many previous standards it covers many areas, for system and device builders as well as system programmers         Sony VGP-BPS13 battery .

Some software developers have trouble implementing ACPI and express concerns about the requirements that bytecode from an external source must be run by the system with full privileges. Linus Torvalds, creator of the Linux kernel, once described it as "a complete design disaster in every way", in relation to his view that "modern PCs are horrible"    Sony VGP-BPS13/B battery .

Microsoft Windows 98 was the first operating system with full support for ACPI , with Windows 2000, Windows XP, Windows Vista, Windows 7, eComStation, FreeBSD, NetBSD,OpenBSD, HP-UX, OpenVMS, Linux and PC versions of SunOS all having at least some support for ACPI Sony VGP-BPS13/S battery .

OSPM responsibilities

ACPI requires that once an OSPM-compatible operating system has activated ACPI on a computer, it then takes over and has exclusive control of all aspects of power management and device configuration   Sony VGP-BPS13A/B battery .

The OSPM implementation must expose an ACPI-compatible environment to device drivers, which exposes certain system, device and processor states.

Global states

The ACPI specification defines the following seven states (so-called global states) for an ACPI-compliant computer-system  Sony VGP-BPS13B/B battery :

  • G0 (S0): Working
  • G1Sleeping subdivides into the four states S1 through S4:
    • S1: All processor caches are flushed, and the CPU(s) stop executing instructions. Power to the CPU(s) and RAM is maintained; devices that do not indicate they must remain on may be powered down  Sony VGP-BPL9 battery .
    • S2: CPU powered off
    • S3: Commonly referred to as StandbySleep, or Suspend to RAM. RAM remains powered
    • S4Hibernation or Suspend to Disk. All content of main memory is saved to non-volatile memory such as a hard drive, and is powered down  Sony VGP-BPS13B/B battery .
  • G2 (S5), Soft Off: G2 is almost the same as G3 Mechanical Off, but some components remain powered so the computer can "wake" from input from the keyboard, clock, modem, LAN, or USBdevice  Sony VGP-BPL15 battery .
  • G3Mechanical Off: The computer's power consumption approaches close to zero, to the point that the power cord can be removed and the system is safe for dis-assembly (typically, only the real-time clock is running off its own small battery)  Dell Inspiron E1505 battery .

Furthermore, the specification defines a Legacy state: the state on an operating system which does not support ACPI. In this state, the hardware and power are not managed via ACPI, effectively disabling ACPI  Dell Latitude E6400 battery .

Device states

The device states D0-D3 are device-dependent:

  • D0 Fully On is the operating state.
  • D1 and D2 are intermediate power-states whose definition varies by device  HP Pavilion dv6000 Battery .
  • D3 Off has the device powered off and unresponsive to its bus.

Processor states

The CPU power states C0-C3 are defined as follows  SONY VAIO VGN-FZ Battery :

  • C0 is the operating state.
  • C1 (often known as Halt) is a state where the processor is not executing instructions, but can return to an executing state essentially instantaneously       SONY VAIO VGN-FZ18 Battery .
  • All ACPI-conformant processors must support this power state. Some processors, such as the Pentium 4, also support an Enhanced C1 state (C1E or Enhanced Halt State) for lower power consumption  SONY VAIO VGN-FZ21E Battery .
  • C2 (often known as Stop-Clock) is a state where the processor maintains all software-visible state, but may take longer to wake up. This processor state is optional  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .
  • C3 (often known as Sleep) is a state where the processor does not need to keep its cache coherent, but maintains other state. Some processors have variations on the C3 state (Deep Sleep, Deeper Sleep, etc.) that differ in how long it takes to wake the processor. This processor state is optional  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Performance states

While a device or processor operates (D0 and C0, respectively), it can be in one of several power-performance states. These states are implementation-dependent, but P0 is always the highest-performance state, with P1 to Pn being successively lower-performance states, up to an implementation-specific limit of n no greater than 16  SONY VAIO VGN-FW21E Battery .

P-states have become known as SpeedStep in Intel processors, as PowerNow! or Cool'n'Quiet in AMD processors, and as PowerSaver in VIA processors.

Hardware Interface

ACPI-compliant systems interact with hardware through either a "Function Fixed Hardware (FFH) Interface" or a platform-independent hardware programming model which relies on platform-specific ACPI Machine Language (AML) provided by the original equipment manufacturer (OEM)    SONY VAIO VGN-NR11Z/S Battery .

Function Fixed Hardware interfaces are platform-specific features, provided by platform manufacturers for the purposes of performance and failure recovery. Standard Intel-based PCs have a fixed function interface defined by Intel SONY VAIO VGN-NR11Z/T Battery ,

which provides a set of core functionality that reduces an ACPI-compliant system's need for full driver stacks for providing basic functionality during boot time or in the case of major system failure  Sony VAIO VGN-FZ21E Battery .

Firmware interface

ACPI defines a large number of tables that provide the interface between an ACPI-compliant operating system and system firmware. These allow description of system hardware in a platform-independent manner, and are presented as either fixed formatted data structures or in AML   Sony VAIO VGN-FW21E Battery .

The main AML table is the DSDT (differentiated system description table).

The Root System Description Pointer is located in a platform-dependent manner, and describes the rest of the tables  Sony VAIO VGN-NR11S/S Battery .

ACPI Component Architecture (ACPICA)

The ACPI Component Architecture (ACPICA) provides an open-source OS-independent reference implementation of the ACPI specification.


The first revision of the ACPI specification was released in December 1996 supporting 16 and 32-bit addressing spaces  Sony VAIO VGN-NR11Z/S Battery .

It wasn't until August 2000 that ACPI received 64-bit address support as well as support for multiprocessor workstations and servers with revision 2.0. In September 2004, revision 3.0 gave the ACPI specification support for SATA connectors, PCI Express bus, >256 multiprocessor support, ambient light sensors and user-presence devices  Sony VAIO VGN-NR11M/S Battery ,

as well as extending the Thermal model beyond the previous processor centric support. The latest of the major publications is that of revision 4.0. Released in June 2009, the 4.0 specification added many new features to the design; most notable are USB 3.0 support, logical processor idling support, and x2APIC support  Sony VAIO VGN-NR11Z/T Battery .

Power management keys are three keys on computer keyboards which control the computer's power management status. They are the Power key, theSleep key, and the Wake key:

  • The Power key is used both to power on and to power off the computer       SONY VAIO VGN-FZ180E Battery .
  • The Sleep key is used to put the computer to sleep, when it uses significantly lower power than when it is active, but can be woken quickly.
  • The Wake key wakes the system from standby   SONY VAIO VGN-FZ220E Battery .

The power saving modes and the transition between them is usually implemented using ACPI.

On computers running Windows Vista, the Windows key can also act as a power management key, and turns on the computer when pressed  SONY VAIO VGN-FZ340E Battery .

Keyboard layout

The placement of the three power management keys on a computer keyboard varies depending on the keyboard's model.

Ideally, these keys should be placed far enough from the rest of the keys       SONY VAIO VGN-FZ430E Battery ,

since the consequences of accidentally pressing one of them while using the computer (with the exception of the Wake key, which does nothing in this situation) can range from being annoying to causing data loss. For instance, if the user has edited a file, but not saved it yet        SONY VAIO VGN-FZ460E Battery ,

on some applications shutting down the system (which happens when a finger slip hits the Power key) can easily lose all the changes (although generally the more used operating systems ask the user to save the file before shut down). While the results of wrongly pressing the Sleep key aren't as extreme (unless the computer has problems returning from sleep)  SONY VAIO VGN-FZ480E Battery,

it can cause problems in real-time games or any application which depends on a network connection.

One common placement for these keys is in the right of the top row of the keyboard, replacing the Print Screen/SysRq, Scroll Lock, and Pause/Break keys, which are moved one row down      SONY VAIO VGN-FZ4000 Battery .

Hereby the 2x3 block of edit and navigation keys is made to occupy the empty space just above the arrow keys. This annoys some people, because it confuses their muscle memory.

Another common placement for these keys is just below the Delete, End, and Page down keys, in the empty space just above the Arrow keys      SONY VAIO VGN-FZ31E Battery .

When used with normal-sized keys, this can cause a high probability of accidental keypresses, especially when the typist is used to a keyboard without any keys on that position, or with the alternate arrangement described above. This leads some people to physically remove the keycaps       SONY VAIO VGN-FZ31B Battery .

Some keyboard models avoid this problem by using keys with a lower height and requiring a higher force to be pressed.

Many keyboards have found a solution to this problem, in that a specific key has to be held down while the power management key is pressed  SONY VAIO VGN-FZ31J Battery .

Often, this is found in the top-right of the keyboard, to the right of the lock button lights, and can be described as "opposite the escape button". With this button, the power, sleep, and wake keys don't do anything when pressed alone, and the function key does nothing, either    SONY VAIO VGN-FZ31M Battery .

Most of the original ADB Apple Macintosh keyboards, as well as the first USB keyboard, had a key to turn the machine on in lieu of a physical power button on the computer itself. The symbol on it was usually a triangle pointing left (?)  SONY VAIO VGN-FZ31Z Battery .

On most keyboards it was located at the extreme upper-right corner, above the function keys and above the right most key, or in the same vertical position and in the center. The power button was replaced with a disc eject button when the Apple Pro Keyboard was introduced, and Apple removed the ability of Macs to be switched on from the keyboard SONY VAIO VGN-FZ38M Battery .

Pressing the power button when running Mac OS brought up the shutdown dialog box, on keyboards with an eject button the combination Control-Eject is used instead (for most x-Power keyboard combinations, x-Eject is used as the replacement combination)  SONY VGP-BPS8 Battery .

Wake-on-LAN (WOL) is an Ethernet computer networking standard that allows a computer to be turned on or woken up by a network message. The message is usually sent by a program executed on another computer on the same local area network SONY VGP-BPS13/S Battery .

Equivalent terms include Wake On WANRemote Wake-upPower On By LANPower Up By LANResume by LANResume on LANWake Up On LAN SONY VGP-BPS13A/B Battery .

In case the computer being woken is communicating via Wi-Fi, a supplementary standard called Wake on Wireless LAN (WoWLAN) must be employed .

The WOL and WoWLAN standards are often supplemented by vendors to provide protocol-transparent on-demand services, for example in the Apple Bonjour wake-on-demand feature  SONY VGP-BPS13B/B Battery .

Technical details

System requirements

Wake-on-LAN support is implemented on the motherboard (BIOS) of a computer and the network interface (firmware), and is consequently not dependent on the operating system (and NIC drivers) running on the hardware   SONY VGP-BPS13A/S Battery .

Some operating systems can control Wake-on-LAN behaviour via hardware drivers. If the network interface is a plug-in card rather than being integrated into the motherboard, the card may need to be connected to the motherboard by a cable. Motherboards with an embedded Ethernet controller which supports Wake-on-LAN do not need a cable   SONY VGP-BPS13AS Battery .

The power supply must meetATX 2.01 specifications.

How it works

Wake-on-LAN is implemented using a special network message called a magic packet. The magic packet contains the MAC address of the destination computer       Dell Inspiron 1320n Battery .

The listening computer waits for a magic packet addressed to it and then initiates system wake-up.

The magic packet is sent on the data link or layer 2 in the OSI model and broadcast to all NICs using the network broadcast address; the IP-address (layer 3 in the OSI model) is not used  Dell Inspiron 1464 Battery .

This is why Wake-on-LAN is platform-independent. Any application, on any platform, can wake up computers running on any other platform.

It is a common misconception that because Wake-on-LAN is built upon broadcast technology it can only be used within the current network subnet. Whilst this is generally the case there are some exceptions  Dell Inspiron 1564 Battery .

In order for Wake-on-LAN to work, parts of the network interface need to stay on. This consumes standby power, much less than normal operating power. If Wake-on-LAN is not needed, disabling it may reduce power consumption slightly while the computer is switched off but still plugged in  Dell Inspiron 1764 Battery .

Magic Packet

The magic packet is a broadcast frame containing anywhere within its payload 6 bytes of all 255 (FF FF FF FF FF FF in hexadecimal), followed by sixteen repetitions of the target computer's 48-bitMAC address  Dell Studio 1450 Battery .

Since the magic packet is only scanned for the string above, and not actually parsed by a full protocol stack, it may be sent as any network- and transport-layer protocol. It is typically sent as a UDPdatagram to port 7 or 9, but actually it can be sent on any port  Dell Studio 1457 Battery .

Limitations of Wake-on-LAN Magic Packets

A standard magic packet has the following basic limitations:

  • Requires destination computer MAC address (also may require a SecureOn password)
  • Does not provide a delivery confirmation  Dell Latitude D610 Battery
  • May not work outside of the local (or the local segment of the) network
  • Require hardware support of Wake-On-LAN on destination computer       Toshiba NB100 Battery

The Wake-on-LAN implementation is designed to be very simple and to be quickly processed by the circuitry present on the network interface card (NIC) with minimal power requirement. Because Wake-on-LAN operates below the protocol layer the MAC address is required and makes IP addresses and DNS names meaningless    Toshiba Satellite M65 battery .

Subnet Directed Broadcasts

A principal limitation of standard broadcast Wake-On-LAN is that broadcast packets are generally not routed. This prevents the technique being used in larger networks or over the internet. Subnet Directed Broadcasts (SDB) may be used to overcome this limitation     Toshiba Satellite M60 battery .

SDB may require changes to intermediate router configuration. Subnet directed broadcasts are treated as normal network packets until processed by the final (local) router. This router converts the packet into a true broadcast packet. This technique allows a broadcast to be initiated on a remote network but requires all intervening routers to forward the SDB Dell Latitude D830 Battery .

When preparing a network to forward SDB packets, care must be taken to filter such that only desired (e.g. WoL) SDB packets are permitted—otherwise the network becomes unprotected against DDoS attacks such as the Smurf Attack  Dell Latitude D620 Battery .

Sending the magic packet

There are many ways to send the magic packet. Software is available for all modern platforms, including Windows, Apple and Linux, plus many smart phones. Also there are web sites on the Internet that allow a magic packet to be sent online without charge  Dell Inspiron Mini 10 Battery .

Example source code for a developer to add Wake-on-LAN to a program is readily available in many computer languages.

Some home routers are able to send magic packets to LAN, for example routers with DD-WRT firmware have Wake On Lan client  Sony VGN-FW11S Battery .

Troubleshooting magic packets

Wake-on-LAN can be a frustrating technology to implement. This is because it requires appropriate BIOS, network card and, sometimes, operating system and router support to function reliably. In some cases hardware may wake from one low power state but not from others    Sony VGN-FW11M Battery .

This means that due to hardware issues the computer may be waking up from the "fully off state" (S5) but doesn't wake from sleep or hibernation.

There are software tools to help with Wake-on-LAN troubleshooting       Sony VGN-FW139E/H battery .

These monitoring tools allow confirmation that the magic packet has arrived at a particular PC. This allows networking issues to be isolated from other hardware issues. In some cases they also confirm that the packet was destined for a specific PC or allow magic packets to be 'promiscuously sniffed' from the network  Dell Latitude E5400 Battery .

In Windows Vista and higher, you can also determine how the OS was powered up. You can use powercfg /lastwake in the CMD prompt and it will list the "Wake Source". The Wake-on-LAN event should also be logged in the System event log Dell Latitude E4200 Battery .

Security Issues

Magic packets are sent via the data link or OSI-2 layer, which can be used or abused by anyone on the same LAN, unless the L2 LAN equipment is capable of (and configured for) filtering such traffic to match site-wide security requirements    Dell Inspiron 300M Battery .

Firewalls may be used to prevent clients within the public WAN from accessing the broadcast addresses of inside LAN segments.

Certain NICs support a security feature called "SecureOn". It allows users to store within the NIC a hexadecimal password of 6 bytesDell Vostro A840 Battery .

Clients have to append this password to the magic packet. TheNIC wakes the system only if the MAC address and password are correct. This security measure significantly decreases the risk of successful brute force attacks, by increasing the search space by 48 bits (6 bytes), up to 296 combinations if the MAC address is entirely unknown Dell Studio 1737 battery .

Still, only a few NIC and router manufacturers support such security features.

Abuse of the Wake-on-LAN feature only allows computers to be switched on; it does not in itself bypass password and other forms of security   Dell Inspiron E1505 battery .

TLS Encryption

Some PCs include technology built into the chipset to improve security for Wake-on-LAN. For example, Intel AMT (a component of Intel vPro technology), includes Transport Layer Security (TLS), an industry-standard protocol that strengthens encryption  Dell RM791 battery .

AMT uses TLS encryption to secure an out-of-band communication tunnel to an AMT-based PC for remote management commands such as Wake-on-LAN. AMT secures the communication tunnelAdvanced Encryption Standard (AES) 128-bit encryption and RSA keys with modulus lengths of 2,048 bits  Dell XPS M1530 battery .

Because the encrypted communication is out-of-band, the PC’s hardware and firmware receive the magic packet before network traffic reaches the software stack for the operating system (OS). Since the encrypted communication occurs “below” the OS level, it is less vulnerable to attacks by viruses, worms, and other threats that typically target the OS level  Dell XPS M2010 battery .

IT shops using Wake-on-LAN through the Intel AMT implementation can wake an AMT PC over network environments that require TLS-based security, such as IEEE 802.1x, Cisco Self Defending Network (SDN), and Microsoft Network Access Protection (NAP) environments   Acer Aspire One battery .

The Intel implementation also works for wireless networks.

Hardware implications

Older motherboards must have a WAKEUP-LINK header onboard connected to the network card via a special 3-pin cable; however, systems supporting the PCI 2.2 standard and with a PCI 2.2 compliant network adapter card do not usually require a Wake-on-LAN cable as the required standby power is relayed through the PCI bus      Toshiba Satellite P10 Battery .

PCI version 2.2 supports PME (Power Management Events). PCI cards send and receive PME signals via the PCI socket directly, without the need for a Wake-on-LAN cable     SONY VGN-FZ210CE Battery .

Wake-on-LAN usually needs to be enabled in the Power Management section of a PC motherboard's BIOS setup utility, although on some systems, such as Apple computers, it is enabled by default. It may also be necessary to configure the computer to reserve power for the network card when the system is shut down     Dell Precision M70 Battery .

In addition, in order to get Wake-on-LAN to work it is sometimes required to enable this feature on the interface card. Details of how to do this depend upon the operating system and the device driver       Toshiba Satellite L305 Battery.

Laptops powered by the Intel Centrino® Processor Technology or newer (with explicit BIOS support) allow waking up the machine using wireless Wake on Wireless LAN (WoWLAN)      Toshiba Satellite T4900 Battery .

In most modern PCs, ACPI is notified of the "waking up" and take control of the Power up. In ACPI, OSPM must record the "wake source" or the device that is causing the power-up. The device being the "Soft" power switch, the NIC (via Wake-on-LAN), the cover being opened, a temperature change, etc     Toshiba PA3399U-2BRS battery .

Other machine states and LAN wakeup signals

In the early days of Wake-on-LAN the situation was relatively simple: a machine was connected to power but switched off, and it was arranged that a special packet be sent to switch the machine on     Toshiba Satellite A200 Battery .

Since then many options have been added and standards agreed upon. A machine can be in 7 power states from S0 (fully on) through S5 (powered down but plugged in) and disconnected from power (G3, Mechanical Off), with names such as "sleep", "standby", and "hibernate"     Toshiba Satellite 1200 Battery .

In some reduced-power modes the system state is stored in RAM and the machine can wake up very quickly; in others the state is saved to disk and the motherboard powered down, taking at least several seconds to awake. The machine can be woken from a reduced-power state by a variety of signals     Toshiba Satellite M300 Battery .

In a particular example, the Gigabyte 8KNXP motherboard with built-in Intel PRO/1000 CT network adapter, there are 3 motherboard BIOS settings and 6 network adapter settings which affect wakeup. The problem is often to prevent the machine waking up immediately after going to a reduced power state     SONY VGP-BPS13A/Q Battery .

The machine's BIOS must be set to allow Wake-on-LAN. To allow wakeup from powered-down state S5, wakeup on PME (Power Management Event) is also required. The Intel adapter allows "Wake on Directed Packet", "Wake on Magic Packet", "Wake on Magic Packet from power off state", and "Wake on Link"       SONY VGP-BPS13A/Q Battery .

Wake on Directed Packet is particularly useful as the machine will automatically come out of standby or hibernation when it is referenced, without the user or application needing to explicitly send a magic packet       SONY VGP-BPS13B/Q Battery .

Unfortunately in many networks waking on directed packet (any packet with the adapter's MAC address or IP address) or on link is likely to cause wakeup immediately after going to a low-power state. Details for any particular motherboard and network adapter are to be found in the relevant manuals    SONY VGP-BPS13B/Q Battery ;

there is no general method. Knowledge of signals on the network may also be needed to prevent spurious wakening.

Unattended operation

For a machine which is normally unattended precautions need to be taken to make the Wake-on-LAN function as reliable as possibleSONY VGP-BPS13/Q Battery .

For a machine procured to work in this way, Wake-on-LAN functionality is an important part of the purchase procedure.

Some machines do not support Wake-on-LAN after they have been disconnected from power (e.g., when power is restored after a power failure)       SONY VGP-BPS13/Q Battery .

Use of an uninterruptible power supply (UPS) will give protection against a short period without power, although the battery will discharge during a prolonged power cut.

Awakening without the operation presence

If a machine that is not designed to support Wake-on-LAN is left powered down after power failure   SONY VGP-BPS21A/B Battery ,

it may be possible to set the BIOS to start it up automatically on restoration of power, so that it is never left in an unresponsive state. A typical BIOS setting is AC back function which may be onoff, or memoryOn is the correct setting in this case; memory, which restores the machine to the state it was in when power was lost, may leave a machine which was hibernating in an unwakeable stateSONY VGP-BPS21/S Battery .

Other problems can affect the ability to start or control the machine remotely: hardware failure of the machine or network, failure of the BIOS settings battery (the machine will halt when started before the network connection is made, displaying an error message and requiring a keypress)       SONY VGP-BPS21B Battery ,

loss of control of the machine due to software problems (machine hang, termination of remote control or networking software, etc.), and virus infection or hard disk corruption. Therefore, the use of a reliable server-class machine with RAID drives, redundant power supplies, etc.      SONY VGP-BPS21A Battery ,

will help to maximize availability. Additionally, a device which can switch the machine off and on again, controlled perhaps by a remote signal, can force a reboot which will clear problems due to misbehaving software      SONY VGP-BPS21 Battery .

For a machine not in constant use, energy can be conserved by putting the machine into low-power RAM standby after a short timeout period. If a connection delay of a minute or two is acceptable, the machine can timeout into hibernation, powered off with its state saved to disk      Sony VGP-BPS21A/B Battery .

Wake on Internet

The computer being woken does not know whether the wakeup signal comes from another machine on the same network or from anywhere else       Sony VGP-BPS21/S Battery .

If the magic packet can be made to reach a computer, it can originate anywhere (e.g., from the Internet). This can be achieved by a Virtual Private Network (VPN), which makes the remote computer appear to be a member of the Local Area Network (LAN)  Sony VGP-BPS21A Battery .

In the absence of a VPN, a computer connected to a router can be woken if a magic packet sent over the Internet is routed to it. This requires any firewall to be set up to allow entry of the Wake-on-LAN signal to a specified port. The port can be forwarded to the computer to be woken up       Sony VGP-BPS21 Battery ;

or some routers permit the packet to be broadcast to the entire LAN . However, some routers do not support this as they will not forward broadcast packets.

Wake-on-Ring (WOR), sometimes referred to as Wake-on-Modem (WOM)   Sony Vaio PCG-5G2L Battery ,

is a specification that allows supported computers and devices to "wake up" or turn on from a sleeping, hibernating or "soft off" state (e.g. ACPI state G1 or G2), and begin operation.

The basic premise is that a special signal is sent over phone lines to the computer through its dial-up modem, telling it to fully power-on and begin operation    Sony Vaio PCG-5G3L Battery .

Common uses were archive databases andBBSes, although hobbyist use was significant.

Fax machines use a similar system, in which they are mostly idle until receiving an incoming fax signal, which spurs operation.

This style of remote operation has mostly been supplanted by Wake-on-LAN, which is newer but works in much the same way  Sony Vaio PCG-5J1L Battery .

Ring Indicator, abbreviated as RI, is a control signal that exists inside an RS-232 serial communications cable that goes between a computer and a modem. The signal is sent from the modem to the computer, typically over pin 9 of a nine-pin (DE9) serial port, or pin 22 over a 25-pin (DB25) port        Sony Vaio PCG-5K2L Battery .

Its purpose is to indicate to the computer that the phone line is ringing.

As implemented in modern PC hardware, a hardware interrupt is generated that can be captured by the processor any time the RI signal changes state       Sony Vaio PCG-5J2L Battery .

This functionality was originally present in the8250 UART - the chip responsible for providing the serial port - which was present in the original IBM PC XT. Virtually all serial hardware for newer PC's, including the popular 16550 UART, has maintained this functionality     Sony Vaio PCG-5K1L Battery .

Having support for this hardware interrupt means that a program or operating system can be informed of a change in state of the RI pin, without requiring the software to constantly "poll" the state of the pin     Sony Vaio PCG-6S2L Battery .

Unlike nearly all of the status pins in the typical PC's 9-pin RS-232 port, RI is a one-way signal from the modem to the computer (or more correctly, the DCE to the DTE) that does not correspond to another signal that carries similar information the opposite waySony Vaio PCG-6S3L Battery .

Conceptually, TXD is paired with RXD, DTR is paired with DSR, and RTS paired with CTS, as each of these signals usually carry the same type of information. The only remaining signal pins are DCD and RI, however both of these signals go in the same direction (tothe computer or DTE) rather than in opposite directions (as the other three mentioned pairs) Sony Vaio PCG-6V1L Battery .

As used on modems

On an external modem with LED lights, the status of the Ring Indicator pin is often coupled to the "AA" (auto answer) light. Normally, the AA light is either off if the modem is not in auto-answer mode, or on if the auto answer mode is enabled (see ATS0 in the Hayes command set)  Sony Vaio PCG-6W1L Battery .

However, when a ring is detected and the RI signal is asserted, the state of the AA light is simultaneously flipped - so it temporarily turns on if auto-answer mode is off, or off if it's on. This doesn't change the auto answer status - rather, it is simply meant as a visual indication of ringing and the assertion of the RI signal Sony Vaio PCG-6W2L Battery .

In practice, most telecommunications programs or server hosts do not actually use the RI signal to detect ringing. Rather, they typically wait for the "RING" message sent to the host over the data pins.

The asserted RI signal lasts nearly exactly as long as the ringing on the telephone line - for example  Sony Vaio PCG-6W3L Battery ,

2.0 seconds per ring burst in North America. The RI signal follows the ringing pattern closely - in fact, it is possible for a computer program to detect distinctive ring patterns from the phone company by monitoring the transitions of the RI signal. If the phone line rings, for example, two short burts and then a long burst, the RI signal will imitate this pattern  Sony Vaio PCG-7111L Battery .

In practice, distinctive ring detection is a feature built in to the command sets of many modern modems. Distinctive ring allows a single phone line to be "shared purpose" whereby it has multiple phone numbers, distinguished only by the ringing pattern, and the modem only answers calls whose ring pattern identify the call as a data call  Sony Vaio PCG-7112L Battery .

As used with other hardware

Even when not used with modems, the signal still exists on a standard PC serial port. Although the signal is unused by most hardware, it is notably used by some older uninterruptible power supplies(UPS's) to signal a power failure state to the computer  Sony Vaio PCG-7113L Battery .

Although newer UPS devices typically send serial data over the "receive data" pins (such is called a "smart" UPS), using the Ring Indicator pin is particularly cheap and simple to implement, because it is essentially a simple signal that can be sent to the computer in the form of either a constant positive or constant negative voltage  Sony Vaio PCG-7133L Battery .

A UPS that uses the Ring Indicator pin to signal a power failure is referred to as a "dumb" UPS[3]. A "mark" (negative voltage) on the Ring Indicator pin indicates a power-fail state. The serial extension cables included with such UPSes are frequently contain conductors only for the Ring Indicator and ground pins   Sony Vaio PCG-7Z2L Battery .


The Ring Indicator pin can also be configured in the BIOS on some computer motherboards to wake the computer from sleep mode. This functionality is known as wake-on-ring, and is conceptually similar to the wake-on-LAN feature found on many Ethernet controllers   Sony Vaio PCG-8Y1L Battery .

A home automation controller from a popular company known as X10 Wireless Technology is a notable example of this type of use. The controller, which connects to the computer's serial port, can be programmed to assert the RI line on the serial port upon detecting a home automation event of the user's choice  Sony Vaio PCG-8Y2L Battery ,

waking up the computer to query the controller for the event ID and then perform any response programmed for the event.

Despite RS232 being considered somewhat of a "legacy" standard, the wake-on-ring functionality is still considered important enough that it is implemented into USB-to-serial converters  Sony Vaio PCG-8Z1L Battery .

When implemented, the USB-to-serial converter remains on standby while the computer is in sleep mode, and sends an ACPI "wake" event over the USB port when the appropriate Ring Indicator transition is detected.

Motherboard BIOSes may refer to this feature with other names or phrases, such as "Power on by external modems" Sony Vaio PCG-8Z2L Battery .

Floating RI interference in serial cables

Some poor quality serial cables can cause computer problems with the Ring Indicator signal  Sony VAIO PCG-5G2L Battery .

This happens if there is inductive interference between the RI line and the RXD/TXD lines when the cable is used with equipment that does not provide any signal on the RI line, and often occurs when using serial extension cords with equipment (which usually carry all 9 or more pins) that only uses a small subset of the serial lines  Sony VAIO PCG-5G3L Battery .

In this scenario, the voltage on the RI line freely "floats ", and can pick up interference from neighboring signals. If the RI line picks up interference from the RXD/TXD lines (which change from high to low rapidly with every bit transmitted, often thousands of times per second)   Sony VAIO PCG-5J1L Battery ,

it can cause the computer to erroneously detect enormous quantities of transitions on the RI line. Each of these transitions generates CPU interrupts and kernel events and can disrupt application software and waste a significant amount of CPU time. If the RI line is unused but carried through a cable next to other wiring         Sony VAIO PCG-5K2L Battery ,

it is important to tie it to either a high or low signal instead of leaving it disconnected and floating. Simply tying it to the output of some other pin on the computer that outputs a steady RS232-level voltage (such as DTR or RTS) will eliminate this problem, regardless of which signal is actually being output on the pin chosen        Sony VAIO PCG-5J2L Battery .

Connecting the pin to ground should be avoided, because the resulting lack of voltage differential (0 volts) is considered an undefined signal in the RS232 standard  Sony VAIO PCG-5K1L Battery .

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22 février 2011 2 22 /02 /février /2011 10:35

VAIOis a sub-brand for many of Sony's computer products. It was originally an acronym for Video Audio Integrated Operation, but since 2008 amended to Visual Audio Intelligence Organizerto celebrate the brand's 10th year anniversary (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk.

The branding was created by Timothy Hanley to distinguish items that encompassed the use of consumer audio and video, as well as being conventional computing products. One example of this was the Sony VAIO W Series personal computer, which functioned as a regular computer and a miniature entertainment center  Dell Studio XPS 1640 Battery.

Although Sony made computers in the 1980s for the Japanese market only, Sony withdrew from the computer business around the turn of the decade. Sony's re-entry to the computer market, this time globally, under the new VAIO brand, started in 1996 with the PCV series of desktops      Dell Vostro 1710 Battery.

The VAIO logo also represents the integration of analog and digital technology. The 'VA' represents an analog wave and the 'IO' represents digital binary code.


Sony is expanding the use of the VAIO label. It can now be found on notebooks, subnotebooks, desktop and media centres  Dell KM958 battery.

Network media solutions by Sony will also carry the VAIO brand.

VAIO notebooks are currently shipped with Microsoft Windows 7 Professional (Business line) or Windows 7 Home Premium, while high-end models sometimes come with Windows 7 Ultimate      Dell Studio 1555 battery.

In mid-2005, all models stopped shipping with a Recovery CD, which was replaced by a hidden partition on the hard drive, accessible at boot via the BIOS or also within Windows via a utility. Pressing [F10] (at the VAIO logo) during boot-up will cause the notebook to boot from the recovery partition      Sony VGP-BPS13 battery;

where the user has the choice of either running hardware diagnostics (without affecting the installed system), or restoring (re-imaging) the hard drive to factory condition (of course, this option will destroy all user installed applications and all data)  Sony VGP-BPS13/B battery.

On first running the system out of the box, VAIO users are prompted to create a set of recovery DVDs, which will be required in case of hard disk failure and replacement with a new drive (normally these would not be required if the system is restored from the hidden partition)    Sony VGP-BPS13/S battery.

Also included as part of the out-of-box experience, are prompts to register at Club VAIO, an online community for VAIO owners and enthusiasts, which also provides automatic driver updates and technical support via email, along with exclusive desktop wallpapers and promotional offers  Sony VGP-BPS13A/B battery.

On recent models, you are also prompted to register your trial versions of Microsoft Office and the installed antivirus software (Norton Anti-Virus on older models, and McAfee Antivirus on newer ones) upon initial boot  Sony VGP-BPS13B/B battery.

VAIO computers come with components from companies such as Intel processors, Seagate Technology, Hitachi, Fujitsu or Toshiba hard drives, Infineon RAM, Atheros and Intel wireless chipsets, Sony (usually made by Hitachi) or Matsushita optical drives, Intel, NVIDIA or ATI graphics processors and Sony speakers  Sony VGP-BPL9 battery.

Recent laptops are being shipped with Qimonda RAM, HP speakers with Realtek High Definition Audio Systems, and optional Dolby Sound Room technology. It has been confirmed that a touch-screen VAIO is planned to be launched as well as support for PlayStation Network  Sony VGP-BPS13B/B battery.


Some Sony VAIO models come with Sony's proprietary XBRITE (also known as ClearBright in Japan and Asia-Pacific region) displays. The first model to introduce this feature is the VAIO TR series    Sony VGP-BPL15 battery.

It is also the first consumer product to utilize such technology. It is a combination of smooth screen, anti-reflection (AR) coating and high-efficiency lens sheet. Sony claims that the smooth finish provides a sharper screen display, the AR coating prevents external light from scattering when it hits the screen        Dell Inspiron E1505 battery,

and the high-efficiency lens sheet provides 1.5 times the brightness improvement over traditional LCD designs, while also extending battery life due to less usage of the LCD backlight. The technology was pioneered by Sony engineer Masaaki Nakagawa, who is in charge of the VAIO TR development      Dell Latitude E6400 battery.

The TX series introduced in September 2005 was the first notebook to implement an LED back-lit screen, which provides lower power consumption and greater color reproduction. This technology has been widely adopted by many other notebook manufacturers now. It was also the first to use a 16:9 aspect ratio screen with 1366x768 resolution  HP Pavilion dv6000 Battery.

The SZ series was the first to use switchable graphics – the motherboard containing an Intel GMCH (Graphics Memory Controller Hub) featuring its own in-built graphics controller (complete memory hub controller and graphics accelerator on the one die) and a separate NVIDIA graphics accelerator chipset directly interfaced with the GMCH  SONY VAIO VGN-FZ Battery.

The GMCH could be used for less power consumption and greater battery life whereas the NVIDIA chipset would be used when greater graphics processing power was needed. A switch is used to toggle between the graphics but required the user to preselect the option before the motherboard could initialize    SONY VAIO VGN-FZ18 Battery.

The Z series has recently replaced the SZ series but does not require a restart of the system to change graphic modes on Windows Vista, it can be done on the fly. This feature has subsequently been used by other manufacturers, including Apple, Asus and Alienware  SONY VAIO VGN-FZ21E Battery.

The high-end AR Series VAIOs were the first to incorporate a Blu-ray Disc burner. This series was designed to be the epitome of high-definition products including a 1080p capable WUXGA (1920 × 1200 pixels) screen, HDMI output and the aforementioned Blu-ray burner      SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

The AR series also includes an illuminated logo below the screen. Blu-ray/HDMI capable models have been the subject of intense promotion since mid-2007, selling with a variety of bundled Blu-ray Discs. The AR series was replaced by the AW series. The AW series incorporates all of these features in a 18.4" 16/9 display       SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Another recent addition to the VAIO series is the TZ model. This new design features a 64GB Solid State Drive (SSD) for rapid boot-ups, quicker application launches and greater durability. If selected, a 250GB Hard Drive may also be included in place of the built-in CD/DVD drive to provide room for additional storage    SONY VAIO VGN-FW21E Battery.

For security this model includes biometric fingerprint sensor and Trusted Platform Module. The TZ offers a Built-in highly miniaturized MOTION EYE camera built into the LCD panel for video conferencing. Additional features include the XBRITE LCD, integrated Wireless Wide Area Network (WWAN) technology and Bluetooth technology  SONY VAIO VGN-NR11S/S Battery.

A selection of media centres were added to the VAIO range in 2006. These monitorless units (identified by a product code prefixed by VGX rather than VGN) are designed to be part of a home entertainment system, which typically take input from a TV tuner card, and output video via HDMI or composite video connection to an ideally high-definition television  SONY VAIO VGN-NR11M/S Battery.

This range so far includes the XL and TP lines. The VGX-TP line is rather visually unique, featuring a circular, 'biscuit-tin' style design with most features obscured behind panels, rather than the traditional set-top box design  SONY VAIO VGN-NR11Z/S Battery.

The VAIO line also features a series of desktop computers, which incorporate motherboard and widescreen LCD monitor into a single unit (in a manner similar to the more recent models of Apple's iMacseries). These are identified by VGC in the product code  SONY VAIO VGN-NR11Z/T Battery.

Bundled software

Sony has been criticized for loading its VAIO laptops with bloatware, or ineffective and unrequested software that supposedly allows the user to immediately use the laptop for multimedia purposes    Sony VAIO VGN-FZ21E Battery.

Dellhad been accused of the same practice, but after strong customer feedback agreed to offer "limited" pre-installed software on its machines.Sony now offers a "Fresh start" option in some regions with some of their business models. With this option, the computer is shipped only with a basic install of Windows and very little of the trial software is installed    Sony VAIO VGN-FW21E Battery.

The default webcam software in VAIO notebooks is ArcSoft WebCam Companion. It offers a set of special effects called Magic-i visual effects, through which users can enhance the images and videos taken through the webcam. It also features the face detection featureSony VAIO VGN-NR11S/S Battery.

Certain other Sony proprietary software such as Click to Disc Editor, VAIO Music Box, VAIO Movie Story, VAIO Media Plus are also included in the recent models. Those shipped with ATI Radeon Video cards feature the Catalyst Control Centre, which enables the user to adjust the various video features such as brightness      Sony VAIO VGN-NR11Z/S Battery,

contrast, resolution etc., and also enables connecting with an external display.

Personal notebooks

All personal notebook models come with Windows 7 Home Premium installed. Unlike the business range, XP downgrade options are not available on all models  Sony VAIO VGN-NR11M/S Battery.

  • AW Series – 18.4" high-end multimedia range, with 1080p resolution screen and SSD options. Replaced the AR series.
  • F Series – 16.4" consumer entertainment range. There are options for a Blu-ray disc reader or burner, and an option for a Full HD widescreen        Sony VAIO VGN-NR11Z/T Battery.
  • The notebook is the second largest in Sony's current range, the first being the VAIO AW series.
  • NW Series – A 15.5" entry level laptop for home users. Successor of the NS Series. Includes an HDMI port and a 16:9 display. The higher-end models include a Blu-ray Disc reader    SONY VAIO VGN-FZ180E Battery.
  • CW Series- A 14" notebook that is customizable compared to the pre-built NW series. Successor to the CS series. Can be customized with up to a Core i5 540M, 8 GB of DDR3 SDRAM, a Blu-ray burner, nVidia graphics and 500 GB hard drive  SONY VAIO VGN-FZ220E Battery.
  • X Series - An 11.1 " ultraportable that uses the Intel Atom Z550 and has 2 GB of DDR2 SDRAM @ 533 MHz. Not only is this the first computer launched in the United States that uses the 2 GHz Atom Z550, but it is also one of the most expensive computers to use an Intel Atom processor, competing with Sony's own VAIO P Series  SONY VAIO VGN-FZ340E Battery.
  • P Series – An 8" ultraportable range that uses a Intel Atom CPU Z520-Z550 dependant on model, and has 2 GB of DDR2 SDRAM @ 533 MHz and a 1600x768(UWXGA)
  • W Series – A 10.1" sub-notebook (netbook), aimed at a young audience  SONY VAIO VGN-FZ430E Battery.
  • Available in White, Brown and Pink using a Intel Atom Processor N450, 1GB DDR2 RAM, 160 GB HDD, Windows XP Home or Windows 7 Home Basic

Business notebooks (VAIO Professional)

Business notebook models usually come with Windows 7 Professional installed (some higher models feature Windows 7 Ultimate  SONY VAIO VGN-FZ460E Battery.

All business models have an XP downgrade option and full driver support).

  • TT Series – Ultra portable 11.1" professional notebook. Successor of the TZ Series. The smallest notebook computer to accommodate a Blu-ray Disc drive at 11 inches  SONY VAIO VGN-FZ480E Battery.
  • Z Series – 13.1" Ultra portable, featuring a 1600 x 900 display an optional 1920 x 1080 (Full High Definition) resolution upgrade and integrated WWAN. (Replaces the high-end models of the SZ Series.)
  • SR Series – 13.3" ultraportable, for home and business use. (Replaces the low-end models of the SZ Series.)SONY VAIO VGN-FZ4000 Battery
  • BZ Series – Robust business notebooks with Trusted Platform Module and biometric fingerprint security technology. (Replaces the BX Series.)  SONY VAIO VGN-FZ31E Battery
  • G Series - 11.1" ultra portable notebook employing Trusted Platform Module technology and biometric fingerprint security features. Weighed only 1.1 kg and was made from CFRP and had an ultra thin LED backlit screen. This notebook brought many technologies that are now on mainstream notebooks to the consumer  SONY VAIO VGN-FZ31B Battery.

From the second quarter of 2008, all higher end models (AW, FW, Z, SR, TT and BZ) have incorporated a cylindrical spine, with no ports on the back of the computer. Generally, the AC adapter port is located on one end of the cylindrical spine, and the power button on the other  SONY VAIO VGN-FZ31J Battery.

Customizable notebooks (configure-to-order)

As of early 2009, Sony offer a customization option on higher-end machines through Sony's high-street and online retail store, Sony Style    SONY VAIO VGN-FZ31M Battery.

Customization options include operating system (64-bit rather than 32-bit versions of Windows), RAM, graphics hardware, and in some models, casing. Configure-to-order machines can be distinguished by the fact their 8-digit product code starts with 54 rather than 27 or 28  SONY VAIO VGN-FZ31Z Battery.

All-in-one desktops

  • L Series
    • LV Series – Full 24" HD LCD display with resolution of 1920x1200 and 16:10 aspect ratio. Blu-ray reader/recorder able to record TV shows on Blu-ray  SONY VAIO VGN-FZ38M Battery
    • LT Series – 22" display with a 2.5 GHz Intel Core 2 Duo processor, 4GB of RAM, a 1TB hard drive, and a built-in Blu-ray burner
    • LN Series – 20.1” X-black LCD display with resolution of 1680x1050 and 16:10 aspect ratio. Blu-ray reader but not recorder    SONY VGP-BPS8 Battery
    • LM Series – 19" display, TV tuner, built-in 1.3 mega pixel cameras with face-tracking software, 2.1-channel speaker system and sub-woofers. Features an Intel Core2 Duo Processor T7250 (2.00 GHz), 2GB DDR2 SDRAM, 250GB HDD, Windows Vista Home Premium, and NVIDIA graphics  SONY VGP-BPS13/S Battery
    • L Series - 24" touch screen displaying 1080p resolution. Intel Core 2 Quad, 6GB RAM, Blu-Ray burner, HDMI port, dual TV tuners, 1TB hard drive, 1GB Nvidia graphics and Windows 7 Home Premium.
  • JS Series – 20.1" integrated lifestyle desktop available in a variety of colors. The chassis design closely resembles that of the Sony Bravia KDL-19M4000 19" LCD HDTV.


Heat problems

On September 4, 2008, Sony announced a worldwide voluntary product inspection and rework program for TZ-series notebook computers manufactured since June 2007. All model numbers beginning with VGN-TZ1 and VGN-TZ2 were eligible, along with some VGN-TZ3 notebooks    SONY VGP-BPS13B/B Battery.

The issue involves "a limited number of units" which could potentially "generate heat around the DC jack inlet and frame of LCD screen, which creates the potential of deformation of the plastic casing"    SONY VGP-BPS13A/S Battery.

In the United States, the service offered is generally on-site, whilst in the rest of the world the service typically involves collection of the notebook by a courier, often DHL, for servicing in a Sony repair center. ChannelWeb reports 100,000 have been recalled  SONY VGP-BPS13AS Battery.

VGN-CS Series Cooling Fan failure

On 9 October 2009, Sony announced:

On affected VAIO notebook computers, the cooling fan will start to make an unusual noise    Dell Inspiron 1320n Battery.

For affected models highlighted in this notice, Sony will offer a free repair service for two years starting from the purchase date.

Concerns regarding Hardware Virtualization

In the past, nearly all Sony VAIO computers have had hardware virtualization technology (VT) disabled at the factory, the exception being the new BZ range        Dell Inspiron 1464 Battery,

which uses an Aptio BIOS by American Megatrends, rather than the customized Phoenix BIOS common on older models. However, on November 3, 2009, Sony released the following information on the Vaio-Link.com website:

A number BIOS updates have been released which provide the option to enable VT in the BIOS    Dell Inspiron 1564 Battery.

If a VT-enabling bios has been published for your VAIO model, you can find it in the Updates section.

The released BIOS updates were provided for most of the VAIO range, and as expected, it will only list the "Enable VT" option in the BIOS if the CPU supports it    Dell Inspiron 1764 Battery.

Lack of Recovery Discs

Sony has designed and produced several models which present the impossibility of creating recovery discs without purchasing an external drive. As Sony does not supply the original recovery discs, a recovery partition is provided which can be accessed by pressing F10    Dell Studio 1450 Battery.

However if the storage media fails, then the partition would be lost. This can present unprecedented issues. e.g. If a customer purchases an American unit and is residing in Australia, the customer cannot obtain recovery discs from Sony unless they are physically on American terra firma        Dell Studio 1457 Battery.

Neither Sony Australia or the customer can order recovery discs for units which are purchased in America. Sony Electronics of America only ships parts and accessories to customers with a U.S. credit card billing and shipping addressDell Latitude D610 Battery.

ThinkPadis a brand of laptop computers originally designed, manufactured and sold by IBM that are known for their boxy black design, which was originally modeled after the Japanese Bento box  (though the current Edge model deviates from this design)Toshiba NB100 Battery.

Since early 2005, the ThinkPad range has been manufactured and marketed by Lenovo, which purchased the IBM personal computer division. Known for their reliability, quality, durability, and performance, ThinkPads are popular with businesses, corporations, and schools  Toshiba Satellite M65 battery;

the ThinkPad has been used in space including being the only laptops certified for use on the International Space Station.


IBM introduced the ThinkPad line in 1992. The name "ThinkPad" had roots in IBM's corporate history and culture  Toshiba Satellite M60 battery.

Thomas J. Watson, Sr., had first introduced "THINK!" as an IBM slogan in the 1920s. For decades IBM distributed small notepads with the word "THINK" emblazoned on a brown leatherette cover to customers and employees. The name ThinkPad was suggested by IBM employee Denny Wainwright, who had a "THINK" notepad in his pocket      Dell Latitude D830 Battery.

The first three ThinkPad models introduced were the 700, 700C, and 700T, which debuted in October 1992. The 700C used the Microsoft Windows 3.1 operating system, 25 MHz 486SLC processor, 120 MB hard disk drive, the industry's first 10.4" TFT color display, 2.2 in (56 mm) × 11.7 in (300 mm) × 8.3 in (210 mm) dimension, and 6.5 lb (2.9 kg) weight, cost US$ 4,350  Dell Latitude D620 Battery.

The design of the commercial versions differed significantly from the prototype's keyboard-less tablet design. The bright red TrackPoint, a kind of pointing stick embedded in the keyboard, enabled the notebook to be used on an airline tray table without a mouse  Dell Inspiron Mini 10 Battery.

As stated above, an IBM researcher conceived the title "ThinkPad" from a corporate-issued leather-bound pocket notebook with the corporate motto 'Think' embossed on the cover. The name faced disagreements from the IBM corporate naming committee because the nomenclature system for the IBM computers was then numerical    Sony VGN-FW11S Battery;

however, the brand name "ThinkPad" was kept as the press showed appreciation for the title. The first ThinkPads were very successful, and soon collected more than 300 awards for design and quality.

The ThinkPad 750 flew aboard the Space Shuttle Endeavour during a mission to repair the Hubble Space Telescope on December 2, 1993      Sony VGN-FW11M Battery.

The ThinkPad 750C's task was to run a NASA test program which determined if radiation inherent in the space environment causes memory anomalies in the 750C or generates other unexpected problems      Sony VGN-FW139E/H battery.

Throughout 2006, a ThinkPad A31p was being used in the Service Module Central Post of the International Space Station and seven ThinkPad A31p laptops were in service in orbit aboard the International Space Station. As of early 2010 the Space Station is equipped with 68 ThinkPad A31 computers plus 32 new Lenovo ThinkPad T61p laptops  Dell Latitude E5400 Battery.

ThinkPads have been praised for exceptional build quality, system reliability, services and design throughout their decade and a half of presence in the consumer market. The original design was a collaboration between Tom Hardy, corporate head of the IBM Design Program    Dell Latitude E4200 Battery,

Italian-based designer Richard Sapper (noted for the design of classic products such as the Tizio lamp for Artemide, office chair for Knoll, kitchenwares for Alessi and ballpoint for Lamy) and Kazuhiko Yamazaki, lead notebook designer at IBM's Yamato Design Center in Japan      Dell Inspiron 300M Battery.

Sapper proposed a design inspired by the Sh?kad? bent?, a traditional black-lacquered Japanese lunch box.

The fold-out butterfly keyboard, which appeared in the ThinkPad 701 series, is widely considered a design masterpiece and is on display at the Museum of Modern Art in New York      Dell Vostro A840 Battery.

The ThinkPad 760 series also included an unusual keyboard design; the keyboard was elevated by two arms riding on small rails on the side of the screen, tilting the keyboard to achieve a more ergonomic design.

The 755CV featured another design quirk        Dell Studio 1737 battery:

the screen could be separated from the lid, allowing it to be used to project the computer display using an overhead projector, before data projectors were commonplace.

Lenovo purchase

In 2005, the Chinese manufacturer Lenovo purchased the ThinkPad brand from IBM in a five-year deal, whereby IBM still helps in the marketing and support of these products          Dell Inspiron E1505 battery.

The following are some of the changes that have been made to the ThinkPad line:

Added Magnesium-alloy chassis roll cage to reduce motherboard flex caused by holding the laptop one handed on a corner.

Added Magnesium-alloy lid roll cage for a sturdier lid while replacing the lid material from magnesium-alloy to plastic for better wireless signal reception        Dell RM791 battery.

Added Carbon Fiber Reinforced Plastic to 15 in (380 mm) ThinkPad Models.

Reintroduced a line of Tablet PCs based on the X-series.

Moved the physical location of GPU to the edge of motherboard near hinge to reduce the chance of damage caused by motherboard flex        Dell XPS M1530 battery.

Introduced Widescreen displays with the Z-series and added Widescreen to the T-series.

Introduced a lower-priced laptop under the Z-series.

Added rubber cushion to the hard drive tray to reduce vibration and to absorb shock  Dell XPS M2010 battery.

Added the Windows key to all 60-series and newer laptops making all the Windows shortcuts possible (although possible before with the keyboard remapping utility).

Official support for Linux on select models.

Added second drainage hole starting with the Z60-series    Acer Aspire One battery.

Ported the ThinkPad keyboard into stand-alone keyboards for desktop PCs in PS/2 or USB.

Expanded usage of the ThinkPad brand name to cover the SL-series, based on designs and chassis from the consumer IdeaPad line.

Expanded usage of the ThinkPad brand name to cover the Thinkpad Edge-series, which used a more modern design with island style keyboard    Toshiba Satellite P10 Battery.

Added an intercooling mechanism that allows the computer's inner workings to remain cool while in use

Placed vents and a draining mechanism that allows any spilled material to drain through the computer without damaging the keyboard      SONY VGN-FZ210CE Battery.

Current product line


This is the current premier line, with all the traditional high-end ThinkPad features available, such as the magnesium alloy rollcage, 7-row keyboard, screen latch, Ultrabay, and ThinkLight. Available in the 14.1" T410, 14.1" thin and light T410s, and 15.6" T510  Dell Precision M70 Battery.


The SL series was originally launched in 2008 as a low-end ThinkPad targeted mainly geared towards small businesses  . These lack several of the traditional ThinkPad features, such as the ThinkLight, magnesium alloy roll cage, Ultrabay, and lid latch, and use a 6-row keyboard with a different layout than the traditional 7-row ThinkPad keyboard  Toshiba Satellite L305 Battery.

Currently, the 14" SL410 and 15.6" SL510 models are offered. A 13.3" model (SL300) was previously offered, but now discontinued.


The L-series replaced the now defunct R-series, and was basically an SL-series with a docking connector and Core i3/i5/i7 CPUs instead of the Core 2 Duo      Toshiba Satellite T4900 Battery.

The chassis is almost identical to the SL-series  , and the two lines share the same repair manuals. The L-series as of January 2011 consists of 2 models, the 14" L412 and the 15.6" L512.


The Edge was released early in 2010 as small business and consumer-end machines    Toshiba PA3399U-2BRS battery.

The design was a radical departure compared to the traditional black boxy ThinkPad design, with glossy surfaces, rounded corners, and silver trim. They were also offered in red, a first for the traditionally black ThinkPads. Like the SL, this was targeted towards small businesses and consumers          Toshiba Satellite A200 Battery,

and lack the roll cage, Ultrabay, lid latch, and ThinkLight of traditional ThinkPads (though the new E420s has a ThinkLight  .) This also introduced an island-style keyboard with a significantly different layout. Currently available in 13.3", 14", and 15.6" sizes, with a 12.5" E220s model coming. An 11.6" Edge 11 model is offered, but not available in the United States  Toshiba Satellite 1200 Battery.


The X-series is the main ultraportable ThinkPad line, offering a lightweight, highly portable laptop with reasonable performance. The 12" X200-series carries all the high-end ThinkPad features like a ThinkLight, lid latch, 7-row keyboard, and rollcage  Toshiba Satellite M300 Battery.

The 11.6" x100e though is all plastic, lacks both the latch and the ThinkLight, and uses a variant of the island keyboard found on the Edge series. It is also offered in red in addition to blue, and white in some countries  . Currently, the 11.6" x100e and the 12.1" X201 are available    SONY VGP-BPS13A/Q Battery.

The 11.6" x120e is coming, and the future X200-series appear to lack a lid latch and use a 12.5" form factor . Formerly, a 13.3" ultrathin model (X300/X301) was offered, along with a thin 12.1" model (X201s), though both have been discontinued  SONY VGP-BPS13A/Q Battery.

X-series Tablet

The X-series tablet is a variant of the 12" X-series models, with low voltage CPUs and a flip-screen tablet screen. These include the traditional ThinkPad features, and have been noted for using a higher quality AFFS-type screen with better viewing angles compared to the screens used on other ThinkPads    SONY VGP-BPS13B/Q Battery.

Currently, the 12.1" X201T model is available, though future models appear to be moving to a 12.5" form factor.


The W-series was introduced in 2008 to replace the p-suffixed performance T-series (e.g. T61p), and are geared towards CAD users, photographers, and others in need of a very high performance system for demanding tasks  SONY VGP-BPS13B/Q Battery.

These are high performance workstation models that offer better screens and faster components like quad core CPUs and higher end workstation graphics compared to the T-series, and are the most powerful ThinkPad laptops out there. These retain the ThinkLight, Ultrabay, roll cage, and lid latch found on the T-series      SONY VGP-BPS13/Q Battery.

Currently available are the 15.6" W510 and 17.1" W701DS, which offers a small secondary display on the right side. The W701DS is the only Thinkpad currently available in the 17" form factor. The W701DS is also the only currently available Lenovo notebook available with a Wacom digitizer built into the palm rest  SONY VGP-BPS13/Q Battery.

A W701 without the dual displays has been offered, but it appears to be discontinued at Lenovo's site as of mid-February 2011.


Traditionally black, ThinkPads have commonly featured magnesium, carbon fiber reinforced plastic or titanium composite cases  SONY VGP-BPS21A/B Battery.

The ThinkPad has introduced many innovations, including theTrackPoint pointing device. ThinkLight, an LED keyboard light at the top of the LCD screen, Active Protection System, an accelerometer sensor which detects when a ThinkPad is falling and shuts the hard drive down to prevent damage      SONY VGP-BPS21/S Battery,

Roll cage design to eliminate motherboard flex, Biometric fingerprint reader, Client Security Solution, which improves security using a built-in TPM and facilitates deployment in corporate environment, ThinkVantage Technologies suite of computer management applications, and drain holes to help reduce damage to the keyboard and components from accidental spillageSONY VGP-BPS21B Battery.

ThinkPad 100-series

The ThinkPad X100e is an entry-level ultraportable notebook. The X100e is available in either the standard non-glossy black or red in color. It contains unusual features like the presence of three USB 2.0 ports, VGA port, Ethernet LAN port, 4-in-1 card reader, headphone and mic combo jack  SONY VGP-BPS21A Battery.

Features an AMD Athlon Neo X2 Single-Core MV-40 (1.60 GHz, 512KB) CPU, support for up to 2GB 667 MHz DDR2 memory. It comes with ATI Radeon HD 3200 IGP 128MB graphic cards, 11.6in HD AntiGlare (1,366 x 768-pixels) display and six-cell lithium-ion  SONY VGP-BPS21 Battery.

ThinkPad 235

The Japan-only ThinkPad 235 (or Type 2607), is an interesting product because it is a progeny of the IBM/Ricoh RIOS project. Also known as Clavius or Chandra2, it contains unusual features like the presence of three PCMCIA slots and the use of dual camcorder batteries as a source of power    Sony VGP-BPS21A/B Battery.

Features an Intel Pentium MMX 233 MHz CPU, support for up to 160 MB of EDO memory, and a built-in 2.5 in (64 mm) hard drive with UDMA support. Hitachi markets Chandra2 as the Prius Note 210.

ThinkPad 240

The ultraportable ThinkPad 240 (X, Z) started with an Intel Celeron and went up to the 600 MHz Intel Pentium III  Sony VGP-BPS21/S Battery.

In models using the Intel 440BX chipset, the RAM was expandable to 320 MB max with a BIOS update. With a 10.4 in (260 mm) screen and an 18 mm (0.71 in) key pitch (a standard key pitch is 19 mm (0.75 in)). They were also one of the first ThinkPad series to contain a built-in Mini PCI card slot (form factor 3b)      Sony VGP-BPS21A Battery.

The 240s have no optical drives and an external floppy drive. An optional extended battery sticks out the bottom like a bar and props up the back of the laptop. Weighing in at 2.9 lb (1.3 kg), these were the smallest and lightest ThinkPads ever made  Sony VGP-BPS21 Battery.

ThinkPad 300-series

The 300-series (300, 310, 340, 350, 360, 365, 380, 385, 390 (all with various sub-series)) was a long-running value series starting at the 386SL/25 processor, all the way to the Pentium III 450. They were lower specified versions of the ThinkPad 700 series, available at a lower price  Sony Vaio PCG-5G2L Battery.

An IBM ThinkPad 310ED and a 760ED, both from the 1996-97 era. For their time, they were very mobile, powerful, and durable. The 760ED boasts the unique flip-up keyboard that was standard on all 760 Thinkpads.

Also a new features with Intel (R) Core I'5 and I'7 series was a Lenovo ThinkPad X300 Tablet PC was using for a work, multitasking and more      Sony Vaio PCG-5G3L Battery.

ThinkPad 500-series

The 500-series (500, 510, 560 (E, X, Z), 570 (E)) were the main line of the ultraportable ThinkPads. Starting with the 486SX2-50 Blue Lightning to the Pentium III 500, these machines had only a hard disk onboard. Any other drives were external (or in the 570's case in the ultrabase)    Sony Vaio PCG-5J1L Battery.

They weighed in at around 4 lb (1.8 kg) and because of their excellent design are still in use today.

ThinkPad 600-series

The 600-series (600, 600E and 600X) are the direct predecessors of the T series, and are known for their portability, comfortable keyboard, and sturdy construction        Sony Vaio PCG-5K2L Battery.

The 600-series packed a 12.1 in (310 mm) SVGA or a 13.3 in (340 mm) XGA TFT LCD, Pentium MMX, Pentium II or III processor, full-sized keyboard, and optical bay into a package weighing roughly 5 lb (2.3 kg). IBM was able to create this light, fully featured machine by using lightweight but strong carbon fiber composite plastics      Sony Vaio PCG-5J2L Battery.

The battery shipped with some 600-series models had a manufacturing defect that left it vulnerable to memory effect and resulted in poor battery life, but this problem can be avoided by use of a third-party battery      Sony Vaio PCG-5K1L Battery.

ThinkPad 700-series

The 700-series (700, 701, 720, 730 (tablet), 750, 755, 760, 765, 770 (many with sub-models)) were the cutting-edge Intel-based ThinkPads. They featured the best screens, largest hard drives and fastest processors available at the time. This was the first successful ThinkPad introduced in 1992 (the first ThinkPad was a tablet PC without a keyboard and a mouse)Sony Vaio PCG-6S2L Battery.

ThinkPad 800-series

The ThinkPad 800-series (800/820/821/822/823/850/851/860) were unique in that they were based on the PowerPC architecture, rather than the Intel x86 architecture. They all used the PowerPC 603e CPU, at speeds of 100 MHz, or 166 MHz in the 860 model  Sony Vaio PCG-6S3L Battery.

The 800 may have used a 603, and it is unclear if the 800 was experimental or not. All units used SCSI 2 instead of IDE hard disks. The units are believed to have all been extremely expensive, as the 850 cost upwards of $12,000. The 800-series can run Windows NT 3.5 (probably 4.0 as well), OS/2, AIX 4.14, SolarisDesktop 2.5.1 PowerPC Edition, and Linux  Sony Vaio PCG-6V1L Battery.

ThinkPad TransNote

The ThinkPad TransNote was a pen-based PC in a laptop. Data could be entered through the keyboard, TrackPoint, paper notepad (with writing sensor below), or the screen via stylus. This ThinkPad expanded on IBM's previous pen based notebooks (360P(E), 730T(E), and 750(P))  Sony Vaio PCG-6W1L Battery.

ThinkPad A-series

The A-series was developed as an allround productivity machine, equipped with hardware powerful enough to make it a desktop replacement. Hence it was the biggest and heaviest ThinkPad series at its time, but also had features not even found in a T-series of the same age. The A-series was dropped in favour of the G-series and R-series  Sony Vaio PCG-6W2L Battery.

ThinkPad G-series

The G-series consisted of only three models, the G40, G41 and G50. Being large and heavy machines, equipped with powerful desktop processors, this line of ThinkPads was consequently specialised in serving as a desktop replacement  Sony Vaio PCG-6W3L Battery.

ThinkPad i-series

The i-series introduced the ThinkLight and were also the first notebooks equipped with Wireless LAN.

ThinkPad R40-series

This line of laptops comprised the R40 and the R40e. These had Mobile Celeron, Pentium 4-M or Pentium M processors, depending on sub-variant  Sony Vaio PCG-7111L Battery.

ThinkPad R50-series

Based on the T40-series, this line of laptops includes the R50, R50e, R50p, R51, R51e and R52. This series of laptops is available with fingerprint-readers and uses many components also found in T40-series models, such as batteries, keyboards and planars (system boards)    Sony Vaio PCG-7112L Battery.

The R51e and the R52, both based on the T43 system board, are the first R-series laptop to utilize DDR2-memory and include a SATA-controller, however uses only ATA-harddrives    Sony Vaio PCG-7113L Battery.

ThinkPad S30 and S31

Japan & Taiwan-only Pentium III model with no CD drive, a 10 in (250 mm) screen, 256 MB Maximum RAM, PCMCIA slot, CF slot, two USB 1.1 ports, Firewire port, RJ11 and RJ45, and a keyboard with English and Japanese shared keys. Battery with built-in stand, long-life 5-hour run      Sony Vaio PCG-7133L Battery.

HDD 20 GB upgradeable to 160 GB tested. Some models have built-in WiFi. BIOS are interchangeable in S30 and S31 and tested to work. The latest known BIOS is 1.82.

ThinkPad W Series

A recent line of mobile workstations designed to suit the needs of CAD/CAM users, 3D and Video artists and photographersSony Vaio PCG-7Z2L Battery.

These are the most powerful ThinkPads ever made. The W701DS has two displays - a 17" main LCD and a 10" slide-out secondary LCD. The W701DS is also available with a Wacom digitizer built into the palm rest.

Thinkpad Edge-series

A series of laptops with focus on more mainstream aesthetics    Sony Vaio PCG-8Y1L Battery.

This series is the first Thinkpad featuring a keyboard that differs from the classic Thinkpad keyboard, and is also currently the only Thinkpad available in a color other than black. It comes in three different colours: glossy red, glossy black and matte black  Sony Vaio PCG-8Y2L Battery.

ThinkPad Z60-series

This is the first ThinkPad laptop to feature a widescreen (16:10 aspect ratio) display. The Z-Series is also the first ThinkPad equipped with a titanium lid (on some models). Integrated WWAN and/or webcam also found on some configurations. The series includes, as of 2006, the Z60 (Z60m and Z60t) and Z61        Sony Vaio PCG-8Z1L Battery;

the latter of which is the first Z-Series ThinkPad with Intel "Yonah" Dual Core Technology. The processor supports Intel VT-x; this is disabled in the BIOS but can be turned on thanks to a BIOS update. Running fully virtualised operating systems via Xen or VMware is therefore possible  Sony Vaio PCG-8Z2L Battery.

ThinkPad T20 series

Comprising the T20, T21, T22 and T23, these were Mobile Pentium III or Mobile Pentium III-M, sub-5 lb (2.3 kg) class machines. Contained processors ranging from 0.18 micrometre (?m) Mobile Pentium III 650 MHz to 0.13 ?m Mobile Pentium III-M 1.20 GHzSony VAIO PCG-5G2L Battery.

Typically had 14.1 in (360 mm) XGA screens, Ultrabay 2000 optical drives, S3 Savage/IX-MV graphics chip and Cirrus Logic CS 4614/22/24 sound chips; although variations along the line existed. Introduced the ThinkLight, a LED mounted inside the upper screen lip that illuminates the keyboard (activated with Fn-PgUp, the extreme diagonal keys)  Sony VAIO PCG-5G3L Battery;

and titanium-reinforced and rubberized screen lids. Used MiniPCI form factor cards, which could be modem and/or Ethernet. With the T23, an internal WiFi antenna became available, so WiFi miniPCI cards could be used. These models did not contain the active hard drive protection or touchpad pointing device which appeared in later models  Sony VAIO PCG-5J1L Battery.

They were clad in black non-slip rubber with embedded glitter. The case lid had tabs along the edge that interlocked with depressions in the lower case when closed, to reduce case flexing. Comparatively more stylish, functional, and rugged machines; and easy to disassemble for repair or upgrades      Sony VAIO PCG-5K2L Battery.

The T23 machine, known internally in IBM as the 'Toronto' model, was the first to include Windows XP.

ThinkPad T30

Features include an Intel Mobile Pentium 4 processor ranging from 1.6 GHz to 2.4 GHz. A T30 may accommodate up to a 2.4 GHz processor with the latest BIOS and Embedded Controller upgrades  Sony VAIO PCG-5J2L Battery.

Graphics are provided by ATI Radeon Mobility 7500 hardware with 16 MB of discrete video memory, which supports external widescreen resolutions. Users have even reported success with output resolutions of 1,920 × 1,200 via DVI on the optional Port Replicator II docking station, although IBM claims a limit of 1,280 × 1,024 due to a weak TMDS transmitter  Sony VAIO PCG-5K1L Battery.

The T30 was available with a 14.1 in (360 mm) screen, with resolutions of 1,024 × 768 and 1,400 × 1,050. DVI video output is available with the optional Port Replicator II docking station, but resolution is officially limited to 1,280 × 1,024  Sony VAIO PCG-5L1L Battery.

Features available include the embedded security subsystem, UltraNav touchpad, 256 MB standard memory (1 GB maximum according to IBM manual, but it has been reported to accept 2 GB of RAM[21]), a 20, 40 or 60 GB hard disk, Ultrabay Plus drive, wireless, and Bluetooth      Sony VAIO PCG-6S2L Battery.

The T30 also contains a miniPCI slot usable for a wireless card. The shell is titanium-reinforced composite. The whole package was a bit heavier and thicker than the T4x series.

ThinkPad T40-series

Includes the T40, T41, T42, T43, and associated pseries (for performance; e.g., T43p)      Sony VAIO PCG-6S3L Battery.

A typical 14.1-inch (360 mm) T4x weighs 4.9 lb (2.2 kg), slightly less than the 600-series, and features an Intel Pentium M Processor (ranging from the Intel Pentium M at 1.73 GHz to the Intel Pentium M 770 at 2.13 GHz), a 14.1 or 15-inch (380 mm) LCD (XGA, SXGA+)      Sony VAIO PCG-6V1L Battery ,

an integrated GPU (Intel Graphics Media Adapter 900) or a discrete GPU (Radeon 7500, 9000, Fire GL 9000, Fire GL T2, and Fire GL V3200 workstation CAD card that is slower in fullscreen video editing and computer games, and most notably 9600 and x300 which are faster for games)      Sony VAIO PCG-6W1L Battery,

and a hard drive ranging in size from 30 to 100 GB with the Active Protection System to protect the hard drive (T41 and later models). p(mobile workstation) models typically offer FireGL CAD graphics, and are also available with a 14 in (360 mm) SXGA+ or a 15 in (380 mm) SXGA+/UXGA FlexView display with wide viewing angle and high density IPS technology  Sony VAIO PCG-6W2L Battery.

These 15-inch (380 mm) display models weigh slightly more than their lesser brethren, with optical drive and battery, at 2.7 kg (5.9 lb). One model of T42 also offered IPS SXGA+ 14 in technology. All T4x models use either 6-cell or 9-cell lithium-ion batteries, as well as an optional 3-cell Ultrabay Slim lithium-polymer battery      Sony VAIO PCG-6W3L Battery.

The 9-cell battery gives a runtime of 5+ hours and a crease allows the laptop to lay flat on an airplane tray-table. Some T42 and T43 models feature a biometric security system with built-in fingerprint reader. Some models also include Bluetooth support  Sony VAIO PCG-7111L Battery.

The T43 model offered DDR2 memory (vs DDR for other T-series machines) but ran hotter and noisier, and so the T42 models were thought to have the best combination of ergonomics and performance. The T40 was IBM's first ThinkPad to use the Pentium M "Banias" CPU      Sony VAIO PCG-7112L Battery.

The T42 employed a Pentium M "Dothan" processor with a 400 MHz frontside bus, while the T43 used a later revision of Dothan running a 533 MHz FSB. Lenovo integrated the ExpressCard into ThinkPad T43 in May 2005.

ThinkPad T60-series

Includes the T60, T61; and associated pseries (for performance; e.g.,. T60p)        Sony VAIO PCG-7113L Battery;

intended as the next generation of the T4x Series ThinkPads; this is the first T-Series ThinkPad to include the Intel Core Duo "Yonah" Technology, and later the Intel Core 2 Duo "Merom" Mobile technology; and the first T-series ThinkPads to come in widescreen resolution    Sony VAIO PCG-7Z1L Battery.

This model has a VMX-enabled BIOS, meaning that running fully virtualised operating systems via Xen or VMware is possible, provided a VMX compatible CPU is installed. The T61, announced in May 2007, features a widescreen resolution as the default resolution, and incorporates the Intel Santa Rosa platform having a fully 64-bit chipset  Sony VAIO PCG-7Z2L Battery.

Like the T60, the T61 also received a CPU core upgrade before its life cycle ended, from "Merom" to "Penryn", both part of the Intel Core 2 Duo line. It is the first T-series ThinkPad to have an integrated web camera (optional), smart card reader (optional), and media card reader (optional)      Sony VAIO PCG-8Y1L Battery.

Furthering innovation founded in the T60, the T61 also sports a top-cover roll cage, aside from the magnesium roll cage inside the main chassis. T61 extra features include a fingerprint reader (some models, also available on T60) and a new improved framing (all T61 models)  WD passport essential (500GB/640GB).

ThinkPad T400 and T500 series

This series succeeded the T61-series. Some T400 models are available with a thinner chassis and thus have an associated sdesignation (for slimor small; e.g., T400s) and lack some rarely used features such as modems  WD passport essential (250GB/320GB).

Notable features include switchable graphics (ability to

switch between discrete and integrated graphics, only in Windows Vista and newer) and optional LED backlit screens. The T400 models include 14.1 in (360 mm) screens but lack digital video out, while the T500 line includes 15.4 in (390 mm) screens and a DisplayPort interface  WD  passport essential SE (750GB/1TB.

T400 and T500 usePenryn core processors and have DDR3 1066 memory by default on all models.

Thinkpad T400s

This is high-end model of T400. This is model is the thinest and lightest model in T series. T400s is based on Intel Penryn platform. The most significant hardware change is the layout of the 7-row keyboard with big ESC and DEL keys  WD  passport elite(250GB/320GB).

ThinkPad T410 and T510 series

The design of setting of this series are based on T400s. This series is based on Intel Calpella platform.

X series

ThinkPad X20-series

Pentium III Mobile, sub-4 lb (1.8 kg) machines. Contained Pentium III-M processors ranging from 500 MHz to 1.13 GHz. 12.1 in (310 mm) XGA screens, and ATI Rage Mobility M1 (X20, X21) or Radeon Mobility M6 (X22, X23, X24) graphics chipsWD passport elite(500GB/640GB).

Used miniPCI form factor cards, which supports modem and/or Ethernet. With the X22 and later machines, provisions for wireless networking support are built into the chassis. Ultrabay 2000 optical drive support can be fitted via the Ultrabase portable docking station option, and extended batteries can give the series a 5-hour running time.2000$WD  passport studio for Mac(320GB/500GB).

ThinkPad X30-series

Pentium III Mobile (X30), Pentium M Banias (X31) or Pentium M Dothan (X32), 12.1 in (310 mm) XGA screens, dedicated Graphic Chip (ATI M6 with 16 MB, which means no shared memory is cut from the RAM), Bluetooth on some models (upgradable), WLAN (802.11b, b/g or even a/b/g), FireWire, CompactFlash card slot  WD  passport studio for Mac(500GB/640GB).

No built-in optical drive. Lots of options like second battery, Mediaslice (for battery and UltraBay), port replicators, docking stations (some with a PCI slot).

ThinkPad X40 Series

An example of the lightweight X series, weighing in at 2.7 lb (1.2 kg), 25% lighter than its predecessor, the X31  WD  Elements series(250GB/320GB).

The last variant of the X40-series, the X41 Tablet, was the first ThinkPad tablet PCsince the original pen-based ThinkPad. It is the lightest 12 in (300 mm) Tablet PC with a keyboard from any manufacturer. It was also the final released ThinkPad designed by IBM before the brand was purchased by Lenovo  WD  Elements SE(500GB/640GB).

ThinkPad X60-series

The X60 is the first X-Series ThinkPad to feature Intel chips using the Intel Core architecture. The Core Duo L2400 (Low Voltage) CPU on the X60s model achieves 7+ hours of battery life on standard benchmarks, and can reach around 10 hours under light use, when using the extended-life battery  WD Elements SE(750GB/1TB).

Note this model lacks a built-in optical drive, unlike the larger T60. The X61, like the T61, also is the first X-series ThinkPad to use Intel's Santa Rosa platform and to be available with a 3G WWAN option. This series includes the Thinkpad Reserve Edition, a 5,000-model limited edition laptop designed for executive class professionals  WD  Elements desktop(500GB/640GB).

It was clad in hand-stitched leather, and came with a three-year 24/7 service warranty.

ThinkPad X300/X301

Codenamed "Kodachi". Released February 26, 2008. Distinguished from other ultraportable laptops by its usage of LED backlighting, removable battery,solid state drive, and integrated DVD burner, it is the flagship model for the X-series  WD  Elements desktop(750GB/1TB).

The ThinkPad X300 used the small form factor Intel GS965 chipset, instead of the standard GM965 along with Intel Core 2 Duo L7100 low voltage CPU with only 12 W TDP. Its successor, the ThinkPad X301 uses the IntelCentrino 2 mobile platform with GS45 chipset and an ultra low voltage CPU  WD  Elements desktop(1.5 TB/2TB).

It also integrates GPS, WWAN, and a webcam in the top lid. The thickest part of the laptop is 0.92 in (2.3 cm) and the thinnest part is 0.73 in (1.9 cm).

ThinkPad X200/X200s

Successor to the X60-series, the ThinkPad X200 laptop leverages the new technology from the X300, including the options of a Solid State Drive (SSD), an optional integrated camera, 12.1" widescreen display  WD  passport essential SE (750GB/1TB)--USB 3.0 ,

optional 3G WWAN, a new 9-cell battery for extended running time up to 9.8 hours, weight as low as 2.95 lb (1.34 kg), and CPU up to 2.66 GHz Intel Core 2 Duo. The X200sis a newer model of the X200 which is lighter and thinner, and has the option of a WXGA+ screen with LED Backlighting for increased battery performance. The X200 series included Tablet PC models  WD  passport essential (500GB/640GB).

Thinkpad X100e series

An entry level ultraportable Thinkpad with an AMD Athlon Neo processor and AMD Vision Pro graphics. The X100e is available in either the standard non-glossy black or red in color  WD  passport for Mac(320GB/500GB).

It contains unusual features like the presence of three USB 2.0 ports, VGA port, Ethernet LAN port, 4-in-1 card reader, heaphone and mic combo jack. CPU options are the AMD Athlon Neo Single-Core MV-40 1.60 GHz, AMD Athlon Neo X2 Dual-Core L335 1.60 GHz, and AMD Turion X2 Dual-Core L625 1.60 GHz  WD  passport for Mac(640GB/1TB).

Support for up to 4GB 667 MHz DDR2 memory. It comes with ATI Radeon HD 3200 IGP 128MB graphic cards, 11.6in HD AntiGlare (1,366 x 768-pixels) display and six-cell lithium-ion.


Both IBM- and Lenovo-made ThinkPads have been recognized by the press for their reliability  My book essential 4 generation  (640GB/1TB).

Laptop Magazinestates that the ThinkPad has the highest-quality laptop computer keyboard available.[26]The ThinkPad was ranked #1 in reliability and support according to PC Magazine's 2007 Survey. The Lenovo ThinkPad is the PC Magazine 2006 Reader's Choice for PC based laptops, and ranked number 1 in Support for PC based laptops  WD  My book essential 4 generation( 1.5TB/2TB).

The ThinkPad Series is the first product line that has received PC World's Hall of Fame award. The ThinkPad X Tablet-series is PC Magazine Editor's Choice for tablet PCs. The 3.5 lb (1.6 kg) ThinkPad X60s is ranked number 1 in ultraportable laptops by PC World. It lasted 8 hours and 21 minutes on a single charge with its 8-cell battery  WD  My book elite( 1TB/1.5TB).

The Lenovo ThinkPad X60s Series is on PC World's Top 100 Products of 2006. The 2005 PC World Reliability and Service survey ranked ThinkPad products ahead of all other brands for reliability. In the 2004 survey, they were ranked second (behind eMachines)  WD  My book studio(1TB/2TB).

Lenovo was named the most environment-friendly company in the electronics industry by Greenpeace in 2007 but has since dropped to place 14 of 17 as of October 2010. Lenovo ThinkPad T60p received the Editor's Choice award for Mobile Graphic Workstation from PC Magazine  WD  My book essential 4 generation( 1.5TB/2TB).

Lenovo ThinkPad X60 is the PC Magazine Editor's Choice among ultra-portable laptops. The Lenovo ThinkPad T400-Series is on PC World's Top 100 Products of 2009.

Users who have previously been using a desktop computer or other notebook brands or are using external keyboards while stationary or own or support other brands criticize Lenovo's choice of Fn andCtrl key placement  WD  My book elite(640GB/2TB).

It has transpired that some VGN-CS series and VGN-BZ series VAIO notebook computers exhibit some uncharacteristic fan noise
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In IBM PC Compatible computers, the basic input/output system (BIOS), also known as the System BIOS, is a de facto standard defining a firmware interface.

The BIOS software is built into the PC, and is the first code run by a PC when powered on ('boot firmware') (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk.

The primary function of the BIOS is to load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware      Dell Studio XPS 1640 Battery.

The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, and loads and executes that software, giving it control of the PC. This process is known as booting, or booting up, which is short for bootstrappingDell Vostro 1710 Battery.

BIOS software is stored on a non-volatile ROM chip built into the system on the mother board. The BIOS software is specifically designed to work with the particular type of system in question, including having a knowledge of the workings of various devices that make up the complementary chipset of the system    Dell KM958 battery.

In modern computer systems, the BIOS chip's contents can be rewritten allowing BIOS software to be upgraded.

A BIOS will also have a user interface (or UI for short). Typically this is a menu system accessed by pressing a certain key on the keyboard when the PC starts. In the BIOS UI, a user can      Dell Studio 1555 battery:

  • configure hardware
  • set the system clock
  • enable or disable system components
  • select which devices are eligible to be a potential boot device      Sony VGP-BPS13 battery
  • set various password prompts, such as a password for securing access to the BIOS UI functions itself and preventing malicious users from booting the system from unauthorized peripheral devices        Sony VGP-BPS13/B battery.

The BIOS provides a small library of basic input/output functions used to operate and control the peripherals such as the keyboard, text display functions and so forth, and these software library functions are callable by external software    Sony VGP-BPS13/S battery.

In the IBM PC and AT, certain peripheral cards such as hard-drive controllers and video display adapters carried their own BIOS extension ROM, which provided additional functionality. Operating systems and executive software, designed to supersede this basic firmware functionality, will provide replacement software interfaces to applications  Sony VGP-BPS13A/B battery.

The role of the BIOS has changed over time; today BIOS is a legacy system, superseded by the more complex EFI (EFI), but BIOS remains in widespread use, and EFI booting has only been supported in Microsoft OS products supporting GPTand Linux Kernels 2.6.1 and greater buildsSony VGP-BPS13B/B battery .

BIOS is primarily associated with the 16-bit, 32-bit, and the beginning of the 64-bit architecture eras, while EFI is used for some newer 32-bit and 64-bit architectures. Today BIOS is primarily used for booting a system and for video initialization (in X.org); but otherwise is not used during the ordinary running of a system  Sony VGP-BPL9 battery,

while in early systems (particularly in the 16-bit era), BIOS was used for hardware access – operating systems (notably MS-DOS) would call the BIOS rather than directly accessing the hardware. In the 32-bit era and later, operating systems instead generally directly accessed the hardware using their own device drivers    Sony VGP-BPS13B/B battery.

However, the distinction between BIOS and EFI is rarely made in terminology by the average computer user, making BIOS a catch-all term for both systems.


The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had only a simple boot loader in their ROM)  Sony VGP-BPL15 battery.

Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M BIOS.

Among other classes of computers, the generic terms boot monitor, boot loaderor boot ROMwere commonly used. Some Sun and PowerPC-based computers use Open Firmware for this purpose      Dell Inspiron E1505 battery.

There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and coreboot.

IBM PC-compatible BIOS chips

In principle, the BIOS in ROM was customized to the particular manufacturer's hardware, allowing low-level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in a standardized way to the operating system  Dell Latitude E6400 battery.

For example, an IBM PC might have had either a monochrome or a color display adapter, using different display memory addresses and hardware - but the BIOS service to print a character on the screen in text mode would be the same  HP Pavilion dv6000 Battery.

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices  SONY VAIO VGN-FZ Battery.

According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOSchips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips  SONY VAIO VGN-FZ18 Battery.

EPROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use EPROM programmers (blasters) to program EPROM chips. Electrically erasable (EEPROM) chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage   SONY VAIO VGN-FZ21E Battery.

BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.

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Beginning with the IBM AT, PCs supported a hardware clock settable through BIOS. It had a century bit which allowed for manually changing the century when the year 2000 happened

SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V

. Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000 by setting the century bit automatically when the clock rolled past midnight, December 31, 1999.

The first flash chips were attached to the ISA bus    SONY VAIO VGN-FW21E Battery.

Starting in 1997, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). In 2006, the first systems supporting a Serial Peripheral Interface (SPI) appeared, and the BIOS flash moved again  SONY VAIO VGN-NR11S/S Battery.

The size of the BIOS, and the capacities of the ROM, EEPROM and other media it may be stored on, has increased over time as new features have been added to the code; BIOS versions now exist with sizes up to 16 megabytes  SONY VAIO VGN-NR11M/S Battery.

Some modern motherboards are including even bigger NAND Flash ROM ICs on board which are capable of storing whole compact operating system distribution like some Linux distributions. For example, some recent ASUS motherboards included SplashTop Linux embedded into their NAND Flash ROM ICs  SONY VAIO VGN-NR11Z/S Battery.

Flashing the BIOS

In modern PCs the BIOS is stored in rewritable memory, allowing the contents to be replaced or 'rewritten'. This rewriting of the contents is sometimes termed 'flashing'. This is done by a special program, usually provided by the system's manufacturerSONY VAIO VGN-NR11Z/T Battery.

A file containing such contents is sometimes termed 'a BIOS image'. A BIOS might be reflashed in order to upgrade to a newer version to fix bugs or provide improved performance or to support newer hardware, or a reflashing operation might be needed to fix a damaged BIOS. A Bios may also be "flashed" by putting the file on the root of a usb drive and bootingSony VAIO VGN-FZ21E Battery.

BIOS chip vulnerabilities

An American Megatrends BIOS registering the “Intel CPU uCode Error” while doing POST, most likely a problem with the POST.

EEPROM chips are advantageous because they can be easily updated by the user; hardware manufacturers frequently issue BIOS updates to upgrade their products, improve compatibility and remove bugsSony VAIO VGN-FW21E Battery.

However, this advantage had the risk that an improperly executed or aborted BIOS update could render the computer or device unusable. To avoid these situations, more recent BIOSes use a "boot block"; a portion of the BIOS which runs first and must be updated separately  Sony VAIO VGN-NR11S/S Battery.

This code verifies if the rest of the BIOS is intact (using hash checksums or other methods) before transferring control to it. If the boot block detects any corruption in the main BIOS, it will typically warn the user that a recovery process must be initiated by booting from removable media (floppy, CD or USB memory) so the user can try flashing the BIOS againSony VAIO VGN-NR11Z/S Battery.

Some motherboards have a backupBIOS (sometimes referred to as DualBIOS boards) to recover from BIOS corruptions.


Some BIOS chips allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its factory preset  Sony VAIO VGN-NR11M/S Battery.

Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan. Overclocking, incorrectly performed, may also cause component temperatures to rise so quickly that they destroy themselves    Sony VAIO VGN-NR11Z/T Battery.

Virus attacks

There are at least three known BIOS attack viruses, two of which were for demonstration purposes.


The first was a virus which was able to erase Flash ROM BIOS content, rendering computer systems unstable. CIH, also known as "Chernobyl Virus", appeared for the first time in mid-1998 and became active in April 1999  SONY VAIO VGN-FZ180E Battery.

It affected systems' BIOS's and often they could not be fixed on their own since they were no longer able to boot at all. To repair this, Flash ROM IC had to be removed from the motherboard to be reprogrammed elsewhere  SONY VAIO VGN-FZ220E Battery.

Damage from CIH was possible since the virus was specifically targeted at the then widespread Intel i430TX motherboard chipset, and the most common operating systems of the time were based on the Windows 9x family allowing direct hardware access to all programs  SONY VAIO VGN-FZ340E Battery.

Modern systems are not vulnerable to CIH because of a variety of chipsets being used which are incompatible with the Intel i430TX chipset, and also other Flash ROM IC types. There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which maySONY VAIO VGN-FZ430E Battery,

in the event of a crash, use a backup BIOS. Also, all modern operating systems like Linux, Mac OS X, Windows NT-based Windows OS like Windows 2000, Windows XP and newer, do not allow user mode programs to have direct hardware access. As a result, as of 2008, CIH has become essentially harmless  SONY VAIO VGN-FZ460E Battery,

at worst causing annoyance by infecting executable files and triggering alerts from antivirus software. Other BIOS viruses remain possible, however ; since Windows users without Windows Vista/7's UAC run all applications with administrative privileges, a modern CIH-like virus could in principle still gain access to hardware  SONY VAIO VGN-FZ480E Battery.

Black Hat 2006

The second one was a technique presented by John Heasman, principal security consultant for UK based Next-Generation Security Software at the Black Hat Security Conference (2006), where he showed how to elevate privileges and read physical memory, using malicious procedures that replaced normal ACPI functions stored in flash memory  SONY VAIO VGN-FZ4000 Battery.

Persistent BIOS Infection

The third one, known as "Persistent BIOS infection", was a method presented in CanSecWest Security Conference (Vancouver, 2009) and SyScan Security Conference (Singapore, 2009) where researchers Anibal Sacco  and Alfredo Ortega, from Core Security Technologies    SONY VAIO VGN-FZ31E Battery,

demonstrated insertion of malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at every start-up, even before the operating system is booted.

The proof-of-concept does not exploit a flaw in the BIOS implementation, but only involves the normal BIOS flashing proceduresSONY VAIO VGN-FZ31B Battery.

Thus, it requires physical access to the machine or for the user on the operating system to be root. Despite this, however, researchers underline the profound implications of their discovery: “We can patch a driver to drop a fully working rootkit. We even have a little code that can remove or disable antivirus  SONY VAIO VGN-FZ31J Battery.”

Firmware on adapter cards

A computer system can contain several BIOS firmware chips. The motherboard BIOS typically contains code to access hardware components absolutely necessary for bootstrapping the system  SONY VAIO VGN-FZ31M Battery,

such as the keyboard (either PS/2 or on a USB human interface device), and storage (floppy drives, if available, and IDE or SATA hard disk controllers). In addition, plug-in adapter cards such as SCSI, RAID,Network interface cards, and video boards often include their own BIOS (e.g. Video BIOS)  SONY VAIO VGN-FZ31Z Battery,

complementing or replacing the system BIOS code for the given component. (This code is generally referred to as an option ROM.) Even devices built into the motherboard can behave in this way; their option ROMs can be stored as separate code on the main BIOS flash chip, and upgraded either in tandem with, or separately to, the main BIOS  SONY VAIO VGN-FZ38M Battery.

An add-in card usually only requires an option ROM if it:

  • Needs to be used before the operating system can be loaded (usually this means it is required in the bootstrapping process), and
  • Is too sophisticated or specific a device to be handled by the main BIOS  SONY VGP-BPS8 Battery

Older PC operating systems, such as MS-DOS (including all DOS-based versions of Microsoft Windows), and early-stage bootloaders, may continue to use the BIOS for input and output. However, the restrictions of the BIOS environment means that modern OSes will almost always use their own device drivers to directly control the hardware  SONY VGP-BPS13/S Battery.

Generally, these device drivers only use BIOS and option ROM calls for very specific (non-performance-critical) tasks, such as preliminary device initialization.

In order to discover memory-mapped ISA option ROMs during the boot process    SONY VGP-BPS13A/B Battery,

PC BIOS implementations scan real memory from 0xC0000 to 0xF0000 on 2 KiB boundaries, looking for a ROMsignature: 0xAA55 (0x55 followed by 0xAA, since the x86 architecture is little-endian). In a valid expansion ROM, this signature is immediately followed by a single byte indicating the number of 512-byte blocks it occupies in real memory  SONY VGP-BPS13B/B Battery.

The next byte contains an offset describing the option ROM's entry point, to which the BIOS immediately transfers control. At this point, the expansion ROM code takes over, using BIOS services to register interrupt vectors for use by post-boot applications, provide a user configuration interface, or display diagnostic information  SONY VGP-BPS13A/S Battery.

There are many methods and utilities for examining the contents of various motherboard BIOS and expansion ROMs, such as Microsoft DEBUG or the UNIX dd.

BIOS boot specification

If the expansion ROM wishes to change the way the system boots (such as from a network device or a SCSI adapter for which the BIOS has no driver code)  SONY VGP-BPS13AS Battery,

it can use the BIOS Boot Specification(BBS) API to register its ability to do so. Once the expansion ROMs have registered using the BBS APIs, the user can select among the available boot options from within the BIOS's user interface    Dell Inspiron 1320n Battery.

This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until the expansion ROMs have finished executing and registering themselves with the BBS API    Dell Inspiron 1464 Battery.

Changing role of the BIOS

Some operating systems, for example MS-DOS, rely on the BIOS to carry out most input/output tasks within the PC. A variety of technical reasons makes it inefficient for some recent operating systems written for 32-bit CPUs such as Linux and Microsoft Windows to invoke the BIOS directly  Dell Inspiron 1564 Battery.

Larger, more powerful, servers and workstations using PowerPC or SPARC CPUs by several manufacturers developed a platform-independent Open Firmware (IEEE-1275), based on the Forth programming language. It is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC CHRP motherboards  Dell Inspiron 1764 Battery.

Later x86-based personal computer operating systems, like Windows NT, use their own, native drivers which also makes it much easier to extend support to new hardware, while the BIOS still relies on a legacy 16-bit real mode runtime interface  Dell Studio 1450 Battery.

There was a similar transition for the Apple Macintosh, where the system software originally relied heavily on the ToolBox—a set of drivers and other useful routines stored in ROM based on Motorola's 680x0 CPUs. These Apple ROMs were replaced by Open Firmware in the PowerPC Macintosh, then EFI in Intel Macintosh computersDell Studio 1457 Battery.

Later BIOS took on more complex functions, by way of interfaces such as ACPI; these functions include power management, hot swapping, thermal management. To quote Linus Torvalds, the task of BIOS is "just load the OS and get the hell out of there"  Dell Latitude D610 Battery.

However BIOS limitations (16-bit processor mode, only 1 MiB addressable space, PC AT hardware dependencies, etc.) were seen as clearly unacceptable for the newer computer platforms. Extensible Firmware Interface (EFI) is a specification which replaces the runtime interface of the legacy BIOS  Toshiba NB100 Battery.

Initially written for the Itanium architecture, EFI is now available for x86 and x86-64 platforms; the specification development is driven by The Unified EFI Forum, an industry Special Interest Group.

Linux has supported EFI via the elilo and GRUB boot loaders  Toshiba Satellite M65 battery.

The Open Source community increased their effort to develop a replacement for proprietary BIOSes and their future incarnations with an open sourced counterpart through the coreboot and OpenBIOS/Open Firmware projects. AMD provided product specifications for some chipsets, and Google is sponsoring the project    Toshiba Satellite M60 battery.

Motherboardmanufacturer Tyan offers coreboot next to the standard BIOS with their Opteron line of motherboards. MSI and Gigabyte Technology have followed suit with the MSI K9ND MS-9282 and MSI K9SD MS-9185 resp. the M57SLI-S4 modelsDell Latitude D830 Battery.

Some BIOSes contain a "SLIC", a digital signature placed inside the BIOS by the manufacturer, for example Dell. This SLIC is inserted in the ACPI table and contains no active code. Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and/or systemrecovery disc containing Windows software  Dell Latitude D620 Battery.

Systems having a SLIC can be activated with an OEM Product Key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating. If a user performs a fresh install of Windows, they will need to have possession of both the OEM key and the digital certificate for their SLIC in order to bypass activation  Dell Inspiron Mini 10 Battery;

in practice this is extremely unlikely and hence the only real way this can be achieved is if the user performs a restore using a pre-customised image provided by the OEM.

Recent Intel processors (P6 and P7) have reprogrammable microcode  Sony VGN-FW11S Battery.

The BIOS may contain patches to the processor code to allow errors in the initial processor code to be fixed, updating the processor microcode each time the system is powered up. Otherwise, an expensive processor swap would be required  Sony VGN-FW11M Battery.

For example, the Pentium FDIV bug became an expensive fiasco for Intel that required a product recall because the original Pentium did not have patchable microcode.

The BIOS business

The vast majority of PC motherboard suppliers license a BIOS "core" and toolkit from a commercial third-party, known as an "independent BIOS vendor" or IBV  Sony VGN-FW139E/H battery.

The motherboard manufacturer then customizes this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer.

Major BIOS vendors include American Megatrends (AMI), Insyde Software, Phoenix Technologies and Byosoft  Dell Latitude E5400 Battery.

Former vendors include Award Software and Microid Research which were acquired byPhoenix Technologies in 1998. Phoenix has now phased out the Award Brand name. General Software, which was also acquired by Phoenix in 2007, sold BIOS for Intel processor based embedded systems  Dell Latitude E4200 Battery.

In computing, booting(also known as "booting up") is a bootstrapping process that starts operating systems when the user turns on a computer system. A boot sequenceis the initial set of operations that the computer performs when power is switched on. The boot loadertypically loads the main operating system for the computer  Dell Inspiron 300M Battery.


The computer word boot is short for "bootstrap" (itself short for "bootstrap load"). The term bootstrap derives from the idiom: to pull oneself up by one's bootstraps  Dell Vostro A840 Battery.

The term refers to the fact that a computer cannot run without first loading software but must be running before any software can be loaded, which seems as impossible as to "pull yourself up by your own bootstraps  Dell Studio 1737 battery."

In computers in the 1950s, pressing a bootstrap button caused a hardwired program to read a bootstrap program from a punched card in a card reader, a magnetic tape in a tape drive, or a magnetic drum unit or magnetic disk drive, and then execute the loaded boot program    Dell Inspiron E1505 battery,

which loaded a larger system of programs from that medium into memory without further help from the human operator. The term "boot" has been used in this sense since at least 1958.  For example, in the IBM 701 computer (1952–1956) which had a "load" button that initiated reading of the first 36-bit word from a punched card, a magnetic tape, or a magnetic drum unit  Dell RM791 battery.

The left 18-bit half-word was then executed as an instruction, which read additional words into memory. Similarly, the IBM 1401 system (c. 1958) used a card reader to load application program from punched cards  Dell XPS M1530 battery.

The 80 characters stored in each punched card were read into memory locations 001 to 080, then the computer would branch to memory location 001 to read its first stored instruction, as read in from the punched card  Dell XPS M2010 battery.

This instruction was always the same: move the information in these first 80 memory locations to an assembly area where the information in punched cards 2, 3, 4, and so on, could be combined to form the stored program    Acer Aspire One battery.

Once this information was moved to the assembly area, the machine would branch to an instruction in location 080 (read a card) and the next card would be read and its information processed. Esentially, the process was one where each subsequent card was "bootstrapped" into memory by the prtevious punched card  Toshiba Satellite P10 Battery.

The CDC 6600 (c. 1964) had a dead startpanel with 144 toggle switches; the dead start switch entered 12 words from the toggle switches to the memory of peripheral processor(PP) 0 and initiated the load sequence. PP 0 loaded the necessary code into its own memory and then initialized the other PP's  SONY VGN-FZ210CE Battery.

The GE 645 (c. 1965) had a "BOOT" button.  It is possible that the contraction from "bootstrap" to "boot" was motivated by an inclination to label the button with fewer, larger characters, or the contraction may follow the familiar habit of contracting words to make them easier to say, and to create insider jargon  Dell Precision M70 Battery.

Some machines, like the Atari ST microcomputer, were "instant-on" with the operating system executing from a ROM. Retrieval of the OS from secondary or tertiary store was thus eliminated as one of the characteristic operations for bootstrapping  Toshiba Satellite L305 Battery.

To accommodate system customization for loading accessories and other support software automatically, as part of the boot process, the Atari's floppy drive was read for the additional components. There was a timeout delay, allowing time to manually insert a floppy, as the system searched for the extra components, which could be avoided by inserting a blank diskToshiba Satellite T4900 Battery.

The Multics operating system (c. 1967) had a boot command. Multics documents also refer to "boot tapes," but it is hard to determine exactly when that term was first used.

In the Unix operating system, the earliest reference for "boot" is probably in The Unix Programmer's Manual, first edition 1971.11.03  Toshiba PA3399U-2BRS battery.

Boot loader

A computer's central processor can only execute program code found in read-only memory (ROM), random access memory (RAM) or an operator's console  Toshiba Satellite A200 Battery.

Modern operating systems and application program code and data are stored on nonvolatile data storage devices, such as hard disk drives, CD, DVD, flash memory cards (like an SD card), USB flash drive, and floppy disk. When a computer is first powered on, it usually does not have an operating system in ROM or RAM  Toshiba Satellite 1200 Battery.

The computer must execute a relatively small program stored in ROM along with the bare minimum of data needed to access the nonvolatile devices from which the operating system programs and data are loaded into RAM  Toshiba Satellite M300 Battery.

The small program that starts this sequence of loading into RAM is known as a bootstrap loader, bootstrapor boot loader. This small boot loader program's only job is to load other data and programs which are then executed from RAM  SONY VGP-BPS13A/Q Battery.

Often, multiple-stage boot loaders are used, during which several programs of increasing complexity sequentially load one after the other in a process of chain loading  SONY VGP-BPS13A/Q Battery.

Early computers (such as the IBM 650, DEC PDP-1 through PDP-8 and early models of the PDP-11) had a row of dials or toggle switches on the front panel to allow the operator to manually enter the boot instructions into memory before transferring control to the CPU, or to directly pass an instruction to the CPU  SONY VGP-BPS13B/Q Battery.

The boot loader would then read in either the second-stage boot loader (called Binary Loaderof paper tape with checksum), or the operating system from an outside storage medium such as paper tape, punched card, or a disk drive  SONY VGP-BPS13B/Q Battery.

Pseudo-assembly code for the bootloader might be as simple as the following eight instructions:

  1. Set the P register to 9
  2. Check paper tape reader ready
  3. If not ready, jump to 2        SONY VGP-BPS13/Q Battery
  4. Read a byte from paper tape reader to accumulator
  5. If end of tape, jump to 9
  6. Store accumulator to address in P register
  7. Increment the P register  SONY VGP-BPS13/Q Battery
  8. Jump to 2

A related example is based on a loader for a 1970's Nicolet Instrument Corporation minicomputer. Note that the bytes of the second-stage loader are read from paper tape in reverse order      SONY VGP-BPS21A/B Battery.

  1. Set the P register to 106
  2. Check paper tape reader ready
  3. If not ready, jump to 2  SONY VGP-BPS21/S Battery
  4. Read a byte from paper tape reader to accumulator
  5. Store accumulator to address in P register
  6. Decrement the P register
  7. Jump to 2  SONY VGP-BPS21B Battery

The length of the second stage loader is such that the final byte overwrites location 7. After the instruction in location 6 executes, location 7 starts the second stage loader executing. The second stage loader then waits for the much longer tape containing the operating system to be placed in the tape reader  SONY VGP-BPS21A Battery.

The difference between the boot loader and second stage loader is the addition of checking code to trap paper tape read errors, a frequent occurrence with the hardware of the time, which in this case was an ASR-33 teletype  SONY VGP-BPS21 Battery.

Some computer systems, upon receiving a boot signal from a human operator or a peripheral device, may load a very small number of fixed instructions into memory at a specific location, initialize at least one CPU, and then point the CPU to the instructions and start their execution  Sony VGP-BPS21A/B Battery.

These instructions typically start an input operation from some peripheral device (which may be switch-selectable by the operator). Other systems may send hardware commands directly to peripheral devices or I/O controllers that cause an extremely simple input operation  Sony VGP-BPS21/S Battery

(such as "read sector zero of the system device into memory starting at location 1000") to be carried out, effectively loading a small number of bootload instructions into memory; a completion signal from the I/O device may then be used to start execution of the instructions by the CPU  Sony VGP-BPS21A Battery.

Smaller computers often use less flexible but more automatic bootload mechanisms to ensure that the computer starts quickly and with a predetermined software configuration. In many desktop computers, for example, the bootstrapping process begins with the CPU executing software contained in ROM  Sony VGP-BPS21 Battery

(for example, the BIOS of an IBM PC) at a predefined address (some CPUs, including the Intel x86 series are designed to execute this software after reset without outside help). This software contains rudimentary functionality to search for devices eligible to participate in booting, and load a small program from a special section (most commonly the boot sector) of the most promising device    Sony Vaio PCG-5G2L Battery.

Boot loaders may face peculiar constraints, especially in size; for instance, on the IBM PC and compatibles, the first stage of boot loaders located on hard drives must fit into the first 446 bytes (or 440 bytes if Windows NT or above has to be supported because NT put 6 byte disk-signature starting from offset 440)Sony Vaio PCG-5G3L Battery

of the Master Boot Record, in order to leave room for the 64-byte partition table and the 2-byte 0xAA55 'signature', which the BIOS requires for a proper boot loader.

Some operating systems, most notably pre-1995 Macintosh systems from Apple      Sony Vaio PCG-5J1L Battery,

are so closely interwoven with their hardware that it is impossible to natively boot an operating system other than the standard one. This is the opposite extreme of the bootload using switches mentioned above; it is highly inflexible but relatively error-proof and foolproof as long as all hardware is working normally      Sony Vaio PCG-5K2L Battery.

A common solution in such situations is to design a bootloader that works as a program belonging to the standard OS that hijacks the system and loads the alternative OS. This technique was used by Apple for its A/UX Unix implementation and copied by various freeware operating systems and BeOS Personal Edition 5      Sony Vaio PCG-5J2L Battery.

The Atari ST also had its operating system in ROM but, by inserting the Spectre GCR cartridge with the Macintosh system ROM in the game slot and turning the Atari on, it could "natively boot" the Macintosh operating system rather than Atari's own TOS system  Sony Vaio PCG-5K1L Battery.

The Atari ST hardware was designed so the cartridge slot could provide native program execution for gaming purposes as a holdover from Atari's legacy making electronic games.

Second-stage boot loader

The small program is most often not itself an operating system, but only a second-stage boot loader, such as GRUB, BOOTMGR, Syslinux, LILO or NTLDR        Sony Vaio PCG-6S2L Battery.

It will then be able to load the operating system properly, and finally transfer execution to it. The operating system will initialize itself, and may load device drivers that are needed for the normal operation of the OS. After that it starts loading normal system programs  Sony Vaio PCG-6S3L Battery.

Many bootloaders (like GRUB, BOOTMGR, LILO, and NTLDR) can be configured to give the user multiple booting choices. These choices can include different operating systems (for dual or multi-booting from different partitions or drives), different versions of the same operating system (in case a new version has unexpected problems)  Sony Vaio PCG-6V1L Battery,

different operating system loading options (e.g., booting into a rescue or safe mode) or some standalone program that can function without an operating system, such as memory testers (e.g., memtest86+) or even games (see List of PC Booter games)      Sony Vaio PCG-6W1L Battery.

Usually a default choice is preselected with a time delay during which you can press a key to change the choice, after which the default choice is automatically run, so normal booting can occur without interaction.

The boot process can be considered complete when the computer is ready to interact with the user, or the operating system is capable of running system programs or application programs      Sony Vaio PCG-6W2L Battery.

Typical modern personal computers boot in about one minute (of which about 15 seconds are taken by a power-on self test (POST) and a preliminary boot loader, and the rest by loading the operating system and other software      Sony Vaio PCG-6W3L Battery.

Time spent after the operating system loading can be considerably shortened by bringing the system with all cores at once, as with coreboot  in as little as 3 seconds, whereas large servers may take several minutes to boot and start all their servicesSony Vaio PCG-7111L Battery.

Many embedded systems must boot immediately. For example, waiting a minute for a digital television or sat-nav to start is generally unacceptable. Therefore such devices have software system in ROM or flash memory so the device can begin functioning immediately    Sony Vaio PCG-7112L Battery.

For these types of embedded system little or no loading is necessary, since the loading can be precomputed and stored on the ROM when the device is made.

Large and complex systems may have boot procedures that proceed in multiple phases, each phase loading a more complex version of itself, until finally the operating system and other software are loaded and ready to execute    Sony Vaio PCG-7113L Battery.

Because operating systems are designed as if they never start or stop, bootload processes sometimes load the operating system, configure themselves as a mere process within that system, and then irrevocably transfer control to the operating system  Sony Vaio PCG-7133L Battery.

The bootload process then terminates normally as any other process would, and the user need not have any awareness of the bootload.

Network booting

Most computers are also capable of booting over a computer network      Sony Vaio PCG-7Z2L Battery.

In this scenario, the operating system is stored on the disk of a server, and certain parts of it are transferred to the client using a simple protocol such as the Trivial File Transfer Protocol. After these parts have been transferred, the operating system then takes over control of the booting process      Sony Vaio PCG-8Y1L Battery.

Boot devices (IBM PC)

The boot device is the device from which the operating system is loaded. A modern PC BIOS supports booting from various devices, typically a local hard disk drive (or one of several partitions on such a disk)        Sony Vaio PCG-8Y2L Battery,

an optical disc drive, a USB device (flash drive, hard disk drive, optical disc drive, etc.), a flash memory card such as an SD card in a multi-media card slot, or a network interface card (usingPXE). Older, less common bootable devices include floppy disk drives, SCSI devices, Zip drives, and LS-120 drives      Sony Vaio PCG-8Z1L Battery.

Typically, the BIOS will allow the user to configure a boot order. If the boot order is set to "firstly, the DVD drive; secondly, the hard disk drive", then the BIOS will try to boot from the DVD drive, and if this fails (e.g. because there is no DVD in the drive), it will try to boot from the local hard drive  Sony Vaio PCG-8Z2L Battery.

For example, on a PC with Windows XP installed on the hard drive, the user could set the boot order to that given above, and then insert a GNU/Linux Live CD in order to try out Linux without having to install an operating system onto the hard drive  Sony VAIO PCG-5G2L Battery.

This is an example of dual booting - the user choosing which operating system to start after the computer has performed its Power On Self Test. In this example of dual booting, the user chooses by inserting or removing the CD from the computer, but it is more common to choose which operating system to boot by selecting from a menu using the computer keyboardSony VAIO PCG-5G3L Battery.

Boot sequence on standard PC (IBM-PC compatible)

Upon starting, a personal computer's x86 CPU runs the instruction located at the memory location CS:IP F000:FFF0 of the BIOS, which is located at the 0xFFFF0 linear address        Sony VAIO PCG-5J1L Battery.

This memory location is close to the end of the 1MB of system memory accessible in real mode. It typically contains a jump instruction that transfers execution to the location of the BIOS start-up program. This program runs a power-on self test (POST) to check and initialize required devices      Sony VAIO PCG-5K2L Battery.

The BIOS goes through a pre-configured list of non-volatile storage devices ("boot device sequence") until it finds one that is bootable. A bootable device is defined as one that can be read from, and the last two bytes of the first sector contain the word 0xAA55 (also known as the boot signature)      Sony VAIO PCG-5J2L Battery.

Once the BIOS has found a bootable device it loads the boot sector to hexadecimal Segment:Offset address 0000:7C00 or 07C0:0000 (maps to the same ultimate address) and transfers execution to the boot code. In the case of a hard disk, this is referred to as the master boot record (MBR) and is often not operating system specific    Sony VAIO PCG-5K1L Battery.

The conventional MBR code checks the MBR's partition table for a partition set as bootable(the one with activeflag set). If an active partition is found, the MBR code loads the boot sector code from that partition and executes it. The boot sector is often operating-system-specific      Sony VAIO PCG-5L1L Battery;

however, in most operating systems its main function is to load and execute the operating system kernel, which continues startup. If there is no active partition, or the active partition's boot sector is invalid, the MBR may load a secondary boot loader which will select a partition (often via user input) and load its boot sector, which usually loads the corresponding operating system kernelSony VAIO PCG-6S2L Battery.

Some systems (particularly newer Macintoshes) use Intel's proprietary EFI. Also coreboot allows a computer to boot without having an over-complicated firmware/BIOS constantly running in system management mode. The legacy 16-bit BIOS interfaces are required by certain x86 operating systems, such as Windows        Sony VAIO PCG-6S3L Battery.

However most boot loaders have 16-bit support for these legacy BIOS systems.

Most PCs, if a BIOS chip is present, will show a screen detailing the BIOS chip manufacturer, copyright held by the chip's manufacturer and the ID of the chip at startup        Sony VAIO PCG-6V1L Battery .

At the same time, it also shows the amount of computer memory available and other pieces of information about the computer.

Power On Self Test (POST)

The computer power-on self-test tests the computer to make sure it meets the necessary system requirements and that all hardware is working properly before starting the remainder of the boot process  Sony VAIO PCG-6W1L Battery.

If the computer passes the POST, the computer may have a single beep (with some computer BIOS suppliers it may beep twice) as the computer starts and the computer will continue to start normally.

Other kinds of boot sequences        Sony VAIO PCG-6W2L Battery

Some other processors have other kinds of boot modes:

1) There are alternative techniques for booting CPUs and microcontrollers        Sony VAIO PCG-6W3L Battery:

  • Some modern CPUs and microcontrollers (for example, TI OMAP) or sometimes even DSPs may have boot ROM with boot code integrated directly into their silicon, so such a processor could perform quite a sophisticated boot sequence on its own and load boot programs from various sources like NAND flash, SD or MMC card and so on  Sony VAIO PCG-7111L Battery.
  • It is hard to hardwire all the required logic for handling such devices, so an integrated boot ROM is used instead in such scenarios. Boot ROM usage enables more flexible boot sequences than hardwired logic could provide. For example, the boot ROM could try to perform boot from multiple boot sources  Sony VAIO PCG-7112L Battery.
  • Also, a boot ROM is often able to load a boot loader or diagnostic program via serial interfaces like UART, SPI, USB and so on. This feature is often used for system recovery purposes when for some reasons usual boot software in non-volatile memory got erased      Sony VAIO PCG-7113L Battery.
  • This technique could also be used for initial non-volatile memory programming when there is clean non-volatile memory installed and hence no software available in the system yet.
  • It is also possible to take control of a system by using a hardware debug interface such as JTAG  Sony VAIO PCG-7Z1L Battery.
  • Such an interface may be used to write the boot loader program into bootable non-volatile memory (e.g. flash) by instructing the processor core to perform the necessary actions to program non-volatile memory. Alternatively, the debug interface may be used to upload some diagnostic or boot code into RAM, and then to start the processor core and instruct it to execute the uploaded code        Sony VAIO PCG-7Z2L Battery.
  • This allows, for example, the recovery of embedded systems where no software remains on any supported boot device, and where the processor does not have any integrated boot ROM. JTAG is a standard and popular interface; many CPUs, microcontrollers and other devices are manufactured with JTAG interfaces (as of 2009)    Sony VAIO PCG-8Y1L Battery.
  • Some microcontrollers provide special hardware interfaces which can't be used to take arbitrary control of a system or directly run code, but instead they allow the insertion of boot code into bootable non-volatile memory (like flash memory) via simple protocols      WD passport essential (500GB/640GB).
  • Then at the manufacturing phase, such interfaces are used to inject boot code (and possibly other code) into non-volatile memory. After system reset, the microcontroller begins to execute code programmed into its non-volatile memory, just like usual processors are using ROMs for booting  WD passport essential (250GB/320GB).
  • Most notably this technique is used by Atmel AVR microcontrollers, and by others as well. In many cases such interfaces are implemented by hardwired logic. In other cases such interfaces could be created by software running in integrated on-chip boot ROM from GPIO pins      WD  passport essential SE (750GB/1TB.

2) Most digital signal processors have the following boot modes:

It is worthwhile mentioning that in case of DSPs there is often a second microprocessor or microcontroller present in the system design, and this is responsible for overall system behavior, interrupt handling, dealing with external events, user interface, etc. while the DSP is dedicated to signal processing tasks only  WD passport elite(500GB/640GB).

In such systems the DSP could be booted by another processor which is sometimes referred as the host processor(giving name to a Host Port). Such a processor is also sometimes referred as the master, since it usually boots first from its own memories and then controls overall s

ystem behavior, including booting of the DSP, and then further controlling the DSP's behaviorWD  passport studio for Mac(320GB/500GB).

An interesting thing here is that the DSP often lacks its own boot memories and relies on the host processor to supply the required code instead. The most notable systems with such a design are cell phones, modems, audio and video players, etc. where a DSP and a CPU/microcontroller are co-existing  WD  passport studio for Mac(500GB/640GB).

Many FPGA chips load their configuration from an external serial EEPROM ("configuration ROM") on power-up.

Initial Program Load

In current IBM mainframe systems, the boot process is known as Initial Program Load(IPL)  WD  Elements series(250GB/320GB).

The term was coined by IBM for the design of the System/360 and continues to be used in those environments today. In systems that share the System/360 heritage—and in some that have been inspired by it, including smaller systems such as the IBM 1130—IPL is a hardware function, not a program run on the system itself        WD  Elements SE(500GB/640GB).

In the smaller S/360 processors, an IPL is initiated by the computer operator by selecting the (three hexadecimal digit) device address using rotary switches on the computer console, followed by pressing the LOADbutton          WD Elements SE(750GB/1TB).

The IPL function in the System/360 and its successors reads 24 bytes from an operator-specified or pre-configured device into memory starting at location zero. The second and third groups of eight bytes are treated as Channel Command Words (CCWs) to continue loading the startup program        WD  Elements desktop(500GB/640GB).

When the I/O channel commands are complete, the first group of eight bytes is then loaded into the Program Status Word (PSW) register and the startup program begins execution at the designated location. The boot device is usually a disk drive, but exactly the same procedure is also used to boot from other devices    WD  Elements desktop(750GB/1TB),

such as tape drives, or even card readers, in a device-independent manner, allowing e.g. the installation of an operating system on a pristine computer from a magnetic distribution tape. Of course, the disk, tape or card deck must contain a special program to load the actual operating system into memory      WD  Elements desktop(1.5 TB/2TB),

a multi-stage procedure similar to most booting procedures (see elsewhere in this article).

A noteworthy variation of this is found on the Burroughs B1700 where there is neither a bootstrap ROM nor a hardwired IPL operation        WD  passport essential SE (750GB/1TB)--USB 3.0 .

Instead, after the system is reset it reads and executes opcodes sequentially from a tape drive mounted on the front panel; this sets up a boot loader in RAM which is then executed          WD  passport essential (500GB/640GB).

However, since this makes few assumptions about the system it can equally well be used to load diagnostic (Maintenance Test Routine) tapes which display an intelligible code on the front panel even in cases of gross CPU failure.


There is some ambiguity in the nomenclature for rebooting, as discussed below  WD  passport for Mac(320GB/500GB).

Hard reboot

A hard reboot(also known as a cold reboot, cold bootor cold start) is when power to a computer is abruptly turned off, then turned back on. This starts the computer without first performing any shut-down procedure (With many operating systems, especially those using disk caches        WD  passport for Mac(640GB/1TB),

after a hard reboot the filesystem may be in an "unclean" state, and an automatic scan of on-disk filesystem structures will be done before normal operation can begin.) It may be caused by power failure, be done by accident, or be done deliberately as a last resort to forcibly retrieve the system from instances of a system freeze  My book essential 4 generation  (640GB/1TB),

critical error or virus-inflicted DoS attack. It can also be used by intruders to access cryptographic keys from RAM, in which case it is called a cold boot attack. The attack relies on the data remanence property of DRAM and SRAM to retrieve memory contents which remain readable in the seconds to minutes after power has been removed      WD  My book essential 4 generation( 1.5TB/2TB).

However, other types of reset also disrupt the operating system in the same manner as power loss:

Soft reboot

A soft reboot(also known as a warm reboot) is restarting a computer under software control, without removing power or (directly) triggering a reset line. It usually, though not always, refers to an orderlyshutdown and restarting of the machine    WD  My book studio(1TB/2TB).

The Control-Alt-Delete key combination on the original PC from Sphere 1 was designed to allow a soft reboot reducing wear on the hardware. This kind of reboot will not usually reset the hard disks, so that they have time to update their write cache to permanent storage      WD  My book essential 4 generation( 1.5TB/2TB).

Hard disks will also keep their configuration (like C/H/S adjustments, HPA, DCO, internal passwords...) over these reboots.

The Linux kernel has optional support for the kexec system call, which transfers execution to a new kernel and skips hardware or firmware reboot    WD  My book elite(640GB/2TB).

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20 février 2011 7 20 /02 /février /2011 14:53

Google Maps (formerly Google Local) is a web mapping service application and technology provided by Google, free (for non-commercial use), that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites via the Google Maps API  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

It offers street maps, a route planner for traveling by foot, car, or public transport and an urban business locator for numerous countries around the world. Google Maps satellite images are not in real time; they are several months or years old   Dell Studio XPS 1640 Battery .

Google Maps uses a close variant of the Mercator projection, so it cannot show areas around the poles. A related product is Google Earth, a stand-alone program which offers more globe-viewing features, including showing polar areas   Dell Vostro 1710 Battery .

Satellite view

Google Maps provides high-resolution satellite images for most urban areas in the United States (including Hawaii, Alaska, Puerto Rico, and the U.S. Virgin Islands), Canada, and the United Kingdom, as well as parts of Australia and many other countries  Dell KM958 battery .

The high-resolution imagery has been used by Google Maps to cover all of Egypt's Nile Valley, Sahara desert and Sinai. Google Maps also covers many cities in the English speaking areas. However, Google Maps is not solely an English maps service, since its service is intended to cover the world   Dell Studio 1555 battery .

Various governments have complained about the potential for terrorists to use the satellite images in planning attacks. Google has blurred some areas for security (mostly in the United States), including the U.S. Naval Observatory area (where the official residence of the Vice President is located), and previously the United States Capitol and the White House  Sony VGP-BPS13 battery .

Other well-known government installations, including Area 51 in the Nevada desert, are visible. Not all areas on satellite images are covered in the same resolution; less populated areas usually get less detail. Some areas may be obscured by patches of clouds  Sony VGP-BPS13/B battery .

With the introduction of an easily pannable and searchable mapping and satellite imagery tool, Google's mapping engine prompted a surge of interest in satellite imagery. Sites were established which feature satellite images of interesting natural and man-made landmarks, including such novelties as "large type" writing visible in the imagery, as well as famous stadia and unique geological formations Sony VGP-BPS13/S battery .

Although Google uses the word satellite, most of the high-resolution imagery is aerial photography taken from aircraft flying at 800–1500 feet rather than from satellites  Sony VGP-BPS13A/B battery .


Google Maps directions work

  • Contiguously on the African mainland, with the exception of Egypt, Lesotho and the Spanish cities of Ceuta and Melilla  Sony VGP-BPS13B/B battery
  • Contiguously in Europe, the Middle East and South Asia: Andorra, Albania, Armenia, Austria, Azerbaijan, Bangladesh, Belgium, Belarus, Bulgaria, Croatia, Czech Republic, Denmark (excluding the Faroe Islands), Estonia, France, Finland, Germany     Sony VGP-BPL9 battery ,
  • Greece, Gibraltar, Hungary, India, Iran, Ireland, Italy, Kazakhstan, Kyrgyzstan, Latvia, Liechtenstein, Lithuania, Luxembourg, FYR Macedonia, Moldova, Monaco, Montenegro, Nepal, The Netherlands, Norway (excluding Svalbard), Pakistan, Poland, Portugal (excluding the Azores and Madeira)   Sony VGP-BPS13B/B battery ,
  • Romania, San Marino, Slovakia, Slovenia, Serbia, Spain (including the Canary Islands and Ceuta and Melilla), Sweden, Switzerland, Tajikistan, Turkey, Turkmenistan, Ukraine, United Kingdom, Uzbekistan, and the Vatican City
  • Contiguously in North America: Canada, and the United States       Sony VGP-BPL15 battery
  • Contiguously in South America: Argentina, Bolivia, Brazil, Chile, Paraguay and Peru (most parts, except e.g. north of San Martín, Piura at the Pacific coast or Iquitos and other places in the Loreto region)
  • Contiguously in Southeast Asia: Cambodia, Laos, Singapore, peninsular Malaysia, Thailand and Vietnam  Dell Inspiron E1505 battery
  • In certain noncontiguous countries and regions: Australia, China, Comoros, Costa Rica, Egypt, Hawaii, Hispaniola (the Dominican Republic and Haiti), Hong Kong, Iceland, Indonesia (Bali, Java, Madura and Sumatra only), Israel (and parts of the West Bank)      Dell Latitude E6400 battery ,
  • Jamaica, Japan, Jordan, South Korea, Lebanon, Macau, Madagascar, Malta, Mauritius, Mexico, New Zealand, Puerto Rico, Réunion, Russia (Moscow area only), Sabah, Sarawak, Seychelles, South Korea (Transit only), Sri Lanka, Taiwan, Turks and Caicos Islands, and the US Virgin Islands     HP Pavilion dv6000 Battery .


Like many other Google web applications, Google Maps uses JavaScript extensively. As the user drags the map, the grid squares are downloaded from the server and inserted into the page      SONY VAIO VGN-FZ Battery .

When a user searches for a business, the results are downloaded in the background for insertion into the side panel and map; the page is not reloaded. Locations are drawn dynamically by positioning a red pin (composed of several partially-transparent PNGs) on top of the map images  SONY VAIO VGN-FZ18 Battery .

A hidden IFrame with form submission is used because it preserves browser history. The site also uses JSON for data transfer rather than XML, for performance reasons. These techniques both fall under the broad Ajax umbrella    SONY VAIO VGN-FZ21E Battery .

Extensibility and customization

As Google Maps is coded almost entirely in JavaScript and XML, some end users have reverse-engineered the tool and produced client-side scripts and server-side hooks which allowed a user or website to introduce expanded or customized features into the Google Maps interface       SONY VAIO VGN-FW21E Battery .

Using the core engine and the map/satellite images hosted by Google, such tools can introduce custom location icons, location coordinates and metadata, and even custom map image sources into the Google Maps interface. The script-insertion tool Greasemonkey provides a large number of client-side scripts to customize Google Maps data  SONY VAIO VGN-NR11S/S Battery.

Combinations with photo sharing websites, such as Flickr, are used to create "memory maps". users have taken advantage of image annotation features to provide personal histories and information regarding particular points of the area  SONY VAIO VGN-NR11M/S Battery .

Google Maps API

Google launched the Google Maps API in June 2005 to allow developers to integrate Google Maps into their websites. It is a free service, and currently does not contain ads, but Google states in their terms of use that they reserve the right to display ads in the future      SONY VAIO VGN-NR11Z/S Battery .

By using the Google Maps API, it is possible to embed Google Maps site into an external website, on to which site specific data can be overlaid. Although initially only a JavaScript API, the Maps API has since expanded to include an API for Adobe Flash applications, a service for retrieving static map images      SONY VAIO VGN-NR11Z/T Battery ,

and web services for performing geocoding, generating driving directions, and obtaining elevation profiles. Over 350,000 web sites use the Google Maps API, making it the most heavily used web application development API     Sony VAIO VGN-FZ21E Battery .

The Google Maps API is free for commercial use providing that the site on which it is being used is publicly accessible and does not charge for access. Sites that do not meet these requirements can purchase Google Maps API Premier      Sony VAIO VGN-FW21E Battery .

The success of the Google Maps API has spawned a number of competing alternatives, including the Yahoo! Maps API, Bing Maps Platform, MapQuest Development Platform, and OpenLayers       Sony VAIO VGN-NR11S/S Battery .

Google Maps for Mobile

In 2006, Google introduced a Java application called Google Maps for Mobile, intended to run on any Java-based phone or mobile device. Many of the web-based site's features are provided in the application       Sony VAIO VGN-NR11Z/S Battery .

On November 28, 2007, Google Maps for Mobile 2.0 was released. It introduced a GPS-like location service that does not require a GPS receiver. The "my location" feature works by utilizing the GPS location of the mobile device, if it is available. This information is supplemented by the software determining the nearest wireless networks and cell sites       Sony VAIO VGN-NR11M/S Battery .

The software then looks up the location of the cell site using a database of known wireless networks and cell sites. The Cell-site location method is used by triangulating the different signal strengths from different cell transmiters and then using their location property (retrieved from the online cell site database) to aid My Location in determining the user's current location  Sony VAIO VGN-NR11Z/T Battery .

Wireless network location method is calculated by discovering the nearby WiFi hotspots and using their location property (retrieved from the online WiFi database, in the same way as the cell site database) to further discover the user's location. The order in which these take precedence is       SONY VAIO VGN-FZ180E Battery :

The software plots the streets in blue that are available with a yellow icon and a green circle around the estimated range of the cell site based on the transmitter's rated power (among other variables). The estimate is refined using the strength of the cell phone signal to estimate how close to the cell site the mobile device is       SONY VAIO VGN-FZ340E Battery .

As of December 15, 2008, this service is available for the following platforms:

  • Android
  • iOS (iPhone/iPod Touch/iPad)
  • Windows Mobile (NOT Windows Phone 7 as of Dec 17 2010)
  • Nokia/Symbian (S60 3rd edition only)      SONY VAIO VGN-FZ430E Battery
  • Symbian OS (UIQ v3)
  • BlackBerry
  • Phones with Java-Platform (MIDP 2.0 and up), for example the Sony Ericsson K800i
  • Palm OS (Centro and newer)
  • Palm webOS (Palm Pre and Palm Pixi)       SONY VAIO VGN-FZ460E Battery

On November 4, 2009, Google Maps Navigation was released in conjunction with Google Android OS 2.0 Eclair on the Motorola Droid, adding voice commands, traffic reports, and street view support. The initial release is limited to the United States  SONY VAIO VGN-FZ480E Battery .

Google Maps Android 2.0.

Google Maps for Android

Cell phones are being increasingly used for navigation assistance. However, written driving instructions are sometimes very confusing to follow. While navigation devices have become a billion dollar industry, Google Maps Navigation for Android 2.0 is free  SONY VAIO VGN-FZ4000 Battery .

Features Provided in the Application:

Google Maps Navigation is free. The drawback of Google Maps for Android is that an internet connection is required to get maps and related information from Google Maps, just like with iPhone’s Google Maps application     SONY VAIO VGN-FZ31J Battery .

Shares of Tom-Tom, Garmin and other navigation service providers fell by almost twenty-five percent after Google's announcement of Google Maps for Navigation. The application was only available initially to Verizon users with Android 2.0 or higher  SONY VAIO VGN-FZ31M Battery .

Google's Navigation was launched in the UK on 20 April 2010 and Australia on 17 November 2010, although it is still unknown when this feature will come to the rest of the world     SONY VAIO VGN-FZ31Z Battery .

Google Maps parameters

In Google Maps, URL parameters are sometimes data-driven in their limits and the user interface presented by the web may or may not reflect those limits. In particular, the zoom level (denoted by thez parameter) supported varies      SONY VAIO VGN-FZ38M Battery .

In less populated regions, the supported zoom levels might stop at around 18. In earlier versions of the API, specifying these higher values might results in no image being displayed. In Western cities, the supported zoom level generally stops at about 20    SONY VGP-BPS8 Battery .

In some isolated cases, the data supports up to 23 or greater, as in these elephants or this view of people at a well in Chad, Africa. Different versions of the API and web interfaces may or may not fully support these higher levels      SONY VGP-BPS13/S Battery .

As of October 2010, the Google map viewer updates its zoom bar to allow the user to zoom all the way when centered over areas that support higher zoom levels.

Development history

Google Maps first started as a C++ program designed to be separately downloaded by users       SONY VGP-BPS13A/B Battery .

Lars and Jens Rasmussen at the Sydney-based company Where 2 Technologies pitched the idea for a purely Web-based product to Google management, changing the method of distribution. In October 2004 the company was acquired by Google Inc where it transformed into the web application Google Maps    SONY VGP-BPS13B/B Battery .

The application was first announced on the Google Blog on February 8, 2005, and was located at Google. It originally only supported users of Internet Explorer and Mozilla web browsers, but support for Opera and Safari was added on February 25, 2005, but currently Opera is removed from the system requirements list        SONY VGP-BPS13A/S Battery .

As of December 2010 Internet Explorer 7.0+,Firefox 3.6+, Safari 3.1+, and Google Chrome are supported. It was in beta for six months before becoming part of Google Local on October 6, 2005.

In April 2005, Google created Google Ride Finder using Google Maps         SONY VGP-BPS13AS Battery .

In June 2005, Google released the Google Maps API. In July 2005, Google began Google Maps and Google Local services for Japan, including road maps. On July 22, 2005, Google released "Hybrid View". Together with this change, the satellite image data was converted from plate carrée to Mercator projection, which makes for a less distorted image in the temperate climes latitudes  Dell Inspiron 1320n Battery .

In July 2005, in honor of the thirty-sixth anniversary of the Apollo Moon landing, Google Moon was launched. In September 2005, in the aftermath of Hurricane Katrina, Google Maps quickly updated its satellite imagery of New Orleans to allow users to view the extent of the flooding in various parts of that city     Dell Inspiron 1464 Battery .

(Oddly, in March 2007, imagery showing hurricane damage was replaced with images from before the storm; this replacement was not made on Google Earth, which still uses post-Katrina imagery)        Dell Inspiron 1564 Battery .

From January 2006, Google Maps featured road maps for the United States, Puerto Rico, Canada, the United Kingdom, Japan, and certain cities in the Republic of Ireland. Coverage of the area aroundTurin was added in time for the 2006 Winter Olympics     Dell Inspiron 1764 Battery .

On January 23, 2006, Google Maps was updated to use the same satellite image database as Google Earth. On March 12, 2006, Google Mars was launched, which features a draggable map and satellite imagery of the planet Mars. In April 2006, Google Local was merged into the main Google Maps site. On April 3, 2006, version 2 of the Maps API was released        Dell Studio 1450 Battery .

On June 11, 2006, Google added geocoding capabilities to the API, satisfying the most developer-requested feature for this service. On June 14, 2006, Google Maps for Enterprise was officially launched. As a commercial service, it features intranet and advertisement-free implementations       Dell Studio 1457 Battery .

In July 2006 Google started including Google Maps business listings in the form of Local OneBoxes in the main Google search results. On December 9 Google integrates the PlusBox in the main search results. On December 19 Google added a feature that lets you add multiple destinations to your driving directions    Dell Latitude D610 Battery .

Beginning in February 2007, buildings and subway stops are displayed in Google Maps "map view" for parts of New York City, Washington, D.C., London, San Francisco, and some other cities.

On January 29, 2007 Local Universal results were upgraded and more data included in the main Google results page  Toshiba NB100 Battery .

On February 28, 2007, Google Traffic info was officially launched to automatically include real-time traffic flow conditions to the maps of 30 major cities of the United States. On March 8, 2007, the Local Business Center was upgraded. On May 16, 2007 Google rolled out Universal search results, including more Map information on the main Google results page   Toshiba Satellite M65 battery .

On May 18, 2007 Google added neighborhood search capabilities. On May 29, 2007, Google driving directions support was added to the Google Maps API. On May 29, 2007, Street View was added, giving a ground-level 360-degree view of streets in some major cities in United States    Toshiba Satellite M60 battery .

On June 19, 2007, reviews were allowed to be added directly to businesses on Google Maps.  On June 28, 2007, draggable driving directions were introduced. On July 31, 2007, support for the hCardmicroformat was announced.  Unfortunately, the implementation is broken    Dell Latitude D830 Battery .

On August 21, 2007, Google announced a simple way to embed Google Maps into other websites.On September 13, 2007, 54 new countries were added to Google Maps in Latin America and Asia. On October 3, 2007, Google Transit was integrated into Google Maps making public transportation routing possible on Google Maps       Dell Latitude D620 Battery .

On October 27, 2007, Google Maps started mapping the geoweb and showing the results in Google Maps. On October 27, 2007, Google Maps added a searchable interface for coupons in the business listings.  On November 27, 2007, "Terrain" view showing basic topographic features was added     Dell Inspiron Mini 10 Battery .

The button for "Hybrid" view was removed, and replaced with a "Show labels" checkbox under the "Satellite" button to switch between "Hybrid" and "Satellite" views.

On January 22, 2008, Google expanded the Local Onebox from 3 business listings to 10    Sony VGN-FW11S Battery .

On February 20, 2008, Google Maps allowed searches to be refined by User Rating & neighborhoods. On March 18, 2008, Google allowed end users to edit business listings and add new places. On March 19, 2008, Google added unlimited category options in the Local Business Center    Sony VGN-FW11M Battery .

On April 2, 2008, Google added contour lines to the Terrain view. In April 2008, a button to view recent Saved Locations was added to the right of the search field. In May 2008, a "More" button was added alongside the "Map", "Satellite", and "Terrain" buttons, permitting access to geographically-related photos on Panoramio and articles on Wikipedia  Sony VGN-FW139E/H battery .

On May 15, 2008, Google Maps was ported to Flash and ActionScript 3 as a foundation for richer internet applications.  On July 15, 2008, walking directions were added.  On August 4, 2008, Street View launched in Japan and Australia. On August 15, 2008, the user interface was redesigned      Dell Latitude E5400 Battery .

On August 29, 2008, Google signed a deal under which GeoEye would supply them with imagery from a satellite, and introduced the Map Maker tool for creation of map data. On September 9, 2008, a reverse business lookup feature was added. On September 23, 2008, information for the New York City Metropolitan Transit Authority was added   Dell Latitude E4200 Battery .

On October 7, 2008, GeoEye-1 took its first image, a bird's-eye view of Kutztown University in Pennsylvania.  On October 26, 2008, reverse geocoding was added to the Maps API. On November 11, 2008, Street View in Spain, Italy, and France was introduced. On November 23, 2008, AIR support for the Maps API for Flash was added         Dell Inspiron 300M Battery .

On November 25, 2008, a new user interface for Street View was introduced. On November 27, 2008, maps, local business information, and local trends for China were introduced. On December 9, 2008, 2x Street View coverage was introduced  Dell Vostro A840 Battery .

In May, 2009, a new Google Maps logo was introduced. In early October 2009, Google replaced Tele Atlas as their primary supplier of geospatial data in the U.S. version of Maps and use their own data.In October 2009, the railroads were redone, featuring a slightly new look and updated, removing older lines      Dell Studio 1737 battery .

Also in the same month, maps in several areas were changed to include paper streets and other odd roads that don't exist, as well as lot lines showing up on the map interface. On February 11, 2010, Google Maps Labs was added. On March 11, 2010, Street View in the United Kingdom, Hong Kong, Macau, and more locations in Japan were launched  Dell Inspiron E1505 battery .

On May 25, 2010, public transportation routing for Denmark was added by integrating with Rejseplanen.dk.

Google's use of Google Maps

The main Google Maps site includes a local search feature (now deprecated), which can be used to locate businesses of a certain type in a geographic area         Dell RM791 battery .

The functionality of the deprecated Google Local Search API is now contained in the Google Places API, currently in developer preview.

Google Ditu

Google Dituwas released to the public on February 9, 2007, and replaced the old Google Bendi. This is the Chinese localized version of Google Maps and Google Local services        Dell XPS M1530 battery .

In order to be compliant with the requirements of Chinese law, Google had to remove or modify some Google Maps features in Google Ditu:

  • Google Ditu does not allow overlay of user-generated content from Panoramio, Youtube, Wikipedia and webcams  Dell XPS M2010 battery .
  • Google Ditu shows the disputed border areas between China and India as being part of China, while on Google Maps those disputed areas are shown inside dotted lines      Acer Aspire One battery .

Google Moon

In honor of the 36th anniversary of the Apollo 11 moon landing on July 20, 1969, Google took public domain imagery of the Moon, integrated it into the Google Maps interface, and created a tool called Google Moon.By default this tool, with a reduced set of features, also displays the points of landing of all Apollo spacecraft to land on the Moon      Toshiba Satellite P10 Battery .

It also included an easter egg, displaying a Swiss cheese design at the highest zoom level, which Google has since removed. A recent collaborative project between NASA Ames Research Center and Google is integrating and improving the data that is used for Google Moon      SONY VGN-FZ210CE Battery .

This is the Planetary Content Project. Google Moon was linked from a special commemorative version of the Google logo displayed at the top of the main Google search page for July 20, 2005 (UTC)   Dell Precision M70 Battery .

Google Mars

Google Mars provides a visible imagery view, like Google Moon, as well as infrared imagery and shaded relief (elevation) of the planet Mars        Toshiba Satellite L305 Battery .

Users can toggle between the elevation, visible, and infrared data, in the same manner as switching between map, satellite, and hybrid modes of Google Maps. In collaboration with NASA scientists at the Mars Space Flight Facility located at Arizona State University, Google has provided the public with data collected from two NASA Mars missions    Toshiba Satellite T4900 Battery ,

Mars Global Surveyor and 2001 Mars Odyssey.

Now, with Google Earth 5 it is possible to access new improved Google Mars data at a much higher resolution, as well as being able to view the terrain in 3D, and viewing panoramas from various Mars landers in a similar way to Google Street View  Toshiba PA3399U-2BRS battery .

Google Sky

On August 27, 2007, Google introduced Google Sky, an online space mapping tool that allows users to pan through a map of the visible universe, using photographs taken by the Hubble Space Telescope       Toshiba Satellite A200 Battery .

Google Ride Finder

Google launched an experimental Google Maps-based tool called Ride Finder, tapping into in-car GPS units for a selection of participating taxi and limousine services. The tool displays the current location of all supported vehicles of the participating services in major U.S      Toshiba Satellite 1200 Battery .

cities, including Chicago and San Francisco, on a Google Maps street map. As of 2009 the tool seems to be discontinued. Not to be confused with carpooling.

Google Transit

In December 2005, Google launched Google Transit on Google Labs, a 20% project of Chris Harrelson and Avichal Garg   Toshiba Satellite M300 Battery .

Google Transit launched initially with support for Portland, Oregon, and now includes hundreds of cities in the United States, Canada, Europe, Asia, Africa, Australia, India(Pune) & New Zealand. The service calculates route, transit time and cost, and can compare the trip to one using a car        SONY VGP-BPS13A/Q Battery .

In October 2007 Google Transit graduated from Google Labs and became fully integrated into Google Maps.


The coverage of Google Transit is publicly available. It is spread worldwide, in hundreds of cities and sometimes in entire countries such as China, Japan, Switzerland        SONY VGP-BPS13A/Q Battery .

The coverage of major cities in the United States and in Canada is almost exhaustive, with a few notable exceptions (as of January 2011) such as Washington, DC.

In some areas, such as the United Kingdom, Google Transit covers only part of the transit agencies         SONY VGP-BPS13B/Q Battery .

For example Transport for London does not provide its data to Google Transit , but some bus companies do, leading to a warning "The coverage may be incomplete" when looking for transit directions in or around London        SONY VGP-BPS13B/Q Battery .

In other areas, Google Transit does not provide public transit directions, but still provides the Transit Layer which overlays the schematic of the transit lines on the map. Notable examples include Paris, Berlin, Mexico City and many other capitals around the world       SONY VGP-BPS13/Q Battery .

Google Biking directions

On March 10, 2010, Google added the possibility to search for biking directions on Google Maps. Optimal routes are calculated from traffic, elevation change, bike paths, bike lanes, and preferred roads for biking        SONY VGP-BPS13/Q Battery .

An optional layer also shows different types of biking paths, from bike-only trails to preferred roads. This service is available in the US  and Canada , and is in beta testing in some other countries such as Singapore     SONY VGP-BPS21A/B Battery .

Google My Maps

In April 2007, My Maps was a new feature added to Google's local search maps. My Maps lets users and businesses create their own map by positioning markers, polylines and polygons onto a map. The interface is a straightforward overlay on the map  SONY VGP-BPS21/S Battery .

A set of eighty-four pre-designed markers is available, ranging from bars and restaurants to webcam and earthquake symbols. Polyline and Polygon color, width and opacity are selectable. Maps modified using My Maps can be saved for later viewing and made public or marked as unlisted, in which case a user will need the saved URL with a 42 character unique ID SONY VGP-BPS21B Battery .

Each element added to a My Map has an editable tag. This tag can contain text, rich text or HTML. Embeddable video and other content can be included within the HTML tag         SONY VGP-BPS21A Battery .

Upon the launch of My Maps there was no facility to embed the created maps into a webpage or blog. A few independent websites have now produced tools to let users embed maps and add further functionality to their maps. This has been resolved with version 2.78       SONY VGP-BPS21 Battery .

Google Street View

On May 25, 2007, Google released Street View, a new feature of Google Maps which provides 360° panoramic street-level views of various U.S. cities        Sony VGP-BPS21A/B Battery .

On this date, the feature only included five cities, but has since expanded to thousands of locations in Australia, Canada, China, the Czech Republic, France, Germany, Hong Kong, India, Italy, Japan, Mexico, New Zealand, South Africa, Spain, Sweden, Switzerland, the Netherlands, Norway, the United Kingdom, and the United States     Sony VGP-BPS21/S Battery .

In August 2008, Australia was added to the Street View feature with nearly all Australian highways, roads and streets having the feature. In addition in that month Japan was added and the Tour de France route was added on July 2 of that year. In December 2008, New Zealand was added to street view         Sony VGP-BPS21A Battery .

The United Kingdom, Australia and New Zealand are the only countries to date with almost all roads and highways featured.

July 2009, Google begins mapping college campuses and surrounding paths and trails. Mexico's main cities and tourist points are added to Street View       Sony VGP-BPS21 Battery .

Street View garnered much controversy after its release because of privacy concerns about the uncensored nature of the panoramic photographs.Since then, Google has begun blurring faces through automatic face detection      Sony Vaio PCG-5G2L Battery .

Google Aerial View

In December 2009 Google released Aerial View, consisting of angled aerial imagery, offering a "bird's eye view" of cities. The first cities available were San Jose and San Diego. This feature was available only to developers via the Google Maps API.  In February 2010 it was introduced as an experimental feature in Google Maps Labs      Sony Vaio PCG-5G3L Battery .

In July 2010 Aerial View was made available in Google Maps in select cities in the United States and worldwide.

The complete list of cities available (as of January 2011) is      Sony Vaio PCG-5J1L Battery :

  • Chile: Santiago and Valparaíso.
  • Germany: Dortmund and Stuttgart.
  • Hungary: Budapest.
  • Italy: Venice.        Sony Vaio PCG-5K2L Battery
  • South Africa: Bloemfontein, Cape Town, Durban, Johannesburg, Nelspruit, Polokwane, Port Elizabeth, Pretoria and Rustenburg Surrounding Area.
  • Spain: Seville       Sony Vaio PCG-5J2L Battery
  • United States: Albuquerque, Austin, Contra Costa County, Escondido, Long Beach, New Orleans, Norfolk, Oakland Area, Oklahoma City, Portland Area, Sacramento Area, Salt Lake City, San Antonio, San Diego Area, San Jose Area, Santa Clara Area, Santa Cruz Area, St. Petersburg, Tucson and Van Nuys     Sony Vaio PCG-5K1L Battery .

Google Latitude

Google Latitude is a feature from Google that lets users share their physical locations with other people. This service is based on Google Maps, specifically on mobile devices. There's an iGoogle widget for Desktops and Laptops as well.  Some concerns have been expressed about the privacy issues raised by the use of the service       Sony Vaio PCG-6S2L Battery .

Google Flu Shot Finder

Google Flu Shot Finder allows users in the United States to identify locations where both the pandemic H1N1/09 virus and seasonal flu vaccines are available near a given address or ZIP code        Sony Vaio PCG-6S3L Battery .

Monopoly City Streets

Monopoly City Streets is a live worldwide version of the game Monopoly using Google Maps as the game board. It was created by Google and Hasbro. The game has now ended        Sony Vaio PCG-6V1L Battery .


Google maps links to the geo-tags placed in Wikipedia articles. It also links to photos with GPS tags from Panoramio.


The Google Maps terms and conditions  state that usage of material from Google Maps is regulated by Google Terms of Service and some additional restrictions        Sony Vaio PCG-6W1L Battery .


Street map overlays, in some areas, may not match up precisely with the corresponding satellite images. The street data may be entirely erroneous, or simply out of date: "The biggest challenge is the currency of data, the authenticity of data," said Google Earth representative Brian McLendon       Sony Vaio PCG-6W2L Battery .

As a result, in March 2008 Google added a feature to edit the locations of houses and businesses.

Restrictions have been placed on Google Maps through the apparent censoring of locations deemed potential security threats. In some cases the area of redaction is for specific buildings, but in other cases, such as Washington, D.C      Sony Vaio PCG-6W3L Battery.,

the restriction is to use outdated imagery. These locations are fully listed on Satellite map images with missing or unclear data.

Google Maps has difficulty processing road data when dealing with cross-boundary situations       Sony Vaio PCG-7111L Battery .

For example, users are unable to obtain a route from Hong Kong to Shenzhen via Shatoujiao, because Google Maps does not display and plan the road map of two overlapping places.

Sometimes objects and even regions on Google Maps are hidden by clouds         Sony Vaio PCG-7112L Battery .

For example, the mast of Arbrå Transmitter near Bollnäs in Sweden is, as of August 25, 2010, hidden under a cloud.

Sometimes the names of geographical locations are inaccurate. An example of this type of error may be found in Google Maps Laona, Wisconsin       Sony Vaio PCG-7113L Battery .

In this instance Google Maps identifies one of the town's two major lakes as "Dawson Lake";  the USGS, State of Wisconsin, and local government maps all identify that map feature as "Scattered Rice Lake". Another example is Samoa, labeled with "Western Samoa", accurate only as recently as 1997       Sony Vaio PCG-7133L Battery .

The Wikipedia option of Google maps has introduced interesting errors by incorporating incorrect or wildly misleading data:

  • Chennai district of India found in the Arctic's Kara Sea      Sony Vaio PCG-7Z2L Battery
  • Giraavaru (Kaafu Atoll) in the Arctic instead of Male' Atoll in the Indian Ocean
  • South Magnetic Pole located very near the North Magnetic Pole

Google collates business listings from multiple on-line and off-line sources      Sony Vaio PCG-8Y1L Battery .

To reduce duplication in the index, Google's algorithm combines listings automatically based on address, phone number, or geocode, but sometimes information for separate businesses will be inadvertently merged with each other, resulting in listings inaccurately incorporating elements from multiple businesses         Sony Vaio PCG-8Y2L Battery .

Google has also recruited volunteers to check and correct ground truth data.

There are some differences in frontier alignments between Google Ditu and Google Maps. On Google Maps, sections of the Chinese border with India and Pakistan are shown with dotted lines, indicating areas or frontiers in dispute  Sony Vaio PCG-8Z1L Battery .

However, Google Ditu shows the Chinese frontier strictly according to Chinese claims with no dotted lines indicating the border with India and Pakistan. For example, the area now administered by India called Arunachal Pradesh (referred to as "South Tibet" by China) is shown inside the Chinese frontier by Google Ditu, with Indian highways ending abruptly at the Chinese claim line  Sony Vaio PCG-8Z2L Battery .

Google Ditu also shows Taiwan and the South China Sea Islands as part of China. As of May 2009, Google Ditu's street map coverage of Taiwan also omits major state organs, such as the Presidential Palace, the five Yuans, and the Supreme Court       Sony VAIO PCG-5G2L Battery .

There are some differences between ditu.google.cn and ditu.google.com. For example, the former does not feature My Maps. On the other hand, while the former displays virtually all text in Chinese, the latter displays most text (user-selectable real text as well as those on map) in English     Sony VAIO PCG-5G3L Battery .

This behavior of displaying English text is not consistent but intermittent – sometimes it is in English, sometimes it is in Chinese. The criteria for choosing which language is displayed is not known     Sony VAIO PCG-5J1L Battery .

In October of 2010, Nicaraguan military commander Edén Pastora stationed Nicaraguan troops on the Isla Calero (in the delta of the San Juan River), justifying his action on the border delineation given by Google Maps      Sony VAIO PCG-5K2L Battery .

The island has long been disputed between Costa Rica and Nicaragua, and the incident renewed border tensions. Bing Maps depicts the island to be on the Costa Rican side of the border. Google has stated it is looking into the issue and will update its data if found to be incorrect      Sony VAIO PCG-5J2L Battery .

Map projection

Google Maps is based on a close variant of the Mercator projection. If the earth were perfectly spherical, the projection would be the same as the Mercator. Google Maps uses the formulæ for the spherical Mercator, but the coordinates of features on Google Maps are the GPS coordinates based on the WGS 84 datum       Sony VAIO PCG-5K1L Battery .

The difference between a sphere and the WGS 84 ellipsoid causes the resultant projection not to be precisely conformal. The discrepancy is meaningless at the global scale but causes maps of local areas to deviate slightly from true ellipsoidal Mercator maps at the same scale        Sony VAIO PCG-5L1L Battery .

Because the Mercator projects the poles at infinity, Google Maps cannot show the poles. Instead it cuts off coverage at 85° north and south. This is not considered a limitation, given the purpose of the service. There are no roads at those latitudes  Sony VAIO PCG-6S2L Battery .

Google Maps Road Trip was a live-streaming documentary produced by Marc Horowitz and Peter Baldes between August 10 and August 18, 2009. The event represented the first virtual live-streaming broadcast cross-country road trip: using only Google Maps, the pair drove from Los Angeles to Richmond, VASony VAIO PCG-6S3L Battery .

They were interviewed by NPR Weekend Edition for their innovative "vacation." They were also mentioned in The New York Times, India's The Economic Times,  The Faster Times  and Readymade Magazine's blog  Sony VAIO PCG-6W1L Battery .

They streamed live on ustream.tv.

Google Maps Road Trip was part of the 6th annual Conflux festival held at New York University in the Steinhardt School of Culture, Education, and Human Development as part of Psy-Geo-Conflux    Sony VAIO PCG-6W1L Battery .

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19 février 2011 6 19 /02 /février /2011 14:00

Windows Internet Explorer (formerly Microsoft Internet Explorer; commonly abbreviated to IE or MSIE), is a series of graphical web browsersdeveloped by Microsoft and included as part of the Microsoft Windows line of operating systems starting in 1995    (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

It was first released as part of the add-on package Plus! for Windows 95 that year. Later versions were available as free downloads, or in service packs, and included in the OEM service releases of Windows 95 and later versions of Windows   Dell Studio XPS 1640 Battery .

IE has been the most widely used web browser since 1999, attaining a peak of about 95% usage share during 2002 and 2003 with IE5 andIE6. Since its peak of popularity, its usage share has declined in the face of renewed competition from other web browsers to 55%, and is slowly trending downward       Dell Vostro 1710 Battery .

Microsoft spent over $100 million per year on IE in the late 1990s, with over 1000 people working on it by 1999.

Since its first release, Microsoft has added features and technologies such as basic table display (in version 1.5); XMLHttpRequest (in version 5), which aids creation of dynamic web pages     Dell KM958 battery ;

and Internationalized Domain Names (in version 7), which allow Web sites to have native-language addresses with non-Latin characters. The browser has also received scrutiny throughout its development for use of third-party technology (such as the source code of Spyglass Mosaic, used without royalty in early versions)  Dell Studio 1555 battery

and security and privacy vulnerabilities, and both the United States and the European Unionhave alleged that integration of IE with Windows has been to the detriment of other browsers.

The latest stable release is Internet Explorer 8, which is available as a free update for Windows XP with Service Pack 2 or later  Sony VGP-BPS13 battery ,

Windows Server 2003with Service Pack 1 or later, Windows Vista, and Windows Server 2008, and is included with Windows 7 and Windows Server 2008 R2. Internet Explorer was originally planned to be omitted from Windows 7 and Windows Server 2008 R2 in Europe but Microsoft later dropped the plans       Sony VGP-BPS13/B battery ,

and instead included a browser ballot screen with the products, allowing users to select a different web browser if they wish.

Versions of Internet Explorer for other operating systems have also been produced, including an embedded OEM version called Internet Explorer Mobilewhich is currently based on IE7      Sony VGP-BPS13/S battery .

Pocket Internet Explorer, later rebranded Internet Explorer Mobile, which is made for Windows Phone 7, Windows CE, and previously Windows Mobile, remains in development alongside the more advanced desktop versions. Internet Explorer for Mac and Internet Explorer for UNIX (Solaris and HP-UX) have been discontinued  Sony VGP-BPS13A/B battery .

he Internet Explorer project was started in the summer of 1994[citation needed] by Thomas Reardon, using source code from Spyglass, Inc.Mosaic, an early commercial web browser with formal ties to the pioneering NCSA Mosaic browser. In late 1994, Microsoft licensed Spyglass Mosaic for a quarterly fee plus a percentage of Microsoft's non-Windows revenues for the software  Sony VGP-BPS13B/B battery .

Although bearing a name similar to NCSAMosaic, Spyglass Mosaic had used the NCSA Mosaic source code sparingly.

Internet Explorer 1 made its debut on August 16, 1995. It was a reworked version of Spyglass Mosaic, which Microsoft had licensed, like many other companies initiating browser development, from Spyglass Inc  Sony VGP-BPL9 battery .

It came with Microsoft Plus! for Windows 95 and the OEM release of Windows 95. It was installed as part of the Internet Jumpstart Kitin Plus!.[11] The Internet Explorer team began with about six people in early development. Internet Explorer 1.5 was released several months later for Windows NT and added support for basic table rendering     Sony VGP-BPS13B/B battery .

However, by including it for free on their OS, they did not have to pay royalties to Spyglass Inc., which resulted in a lawsuit and a multi-million USD settlement.

Internet Explorer 2 was released for Windows 95, Windows NT 3.5, and NT 4.0 on November 22, 1995 (following a 2.0 beta in October). It featured support for SSL, cookies, VRML, RSA, and Internet newsgroups       Sony VGP-BPL15 battery .

Version 2 was also the first release for Windows 3.1 and Macintosh System 7.0.1 (PPC or 68k), although the Mac version was not released until January 1996 for PPC, and April for 68k.Version 2.1 for the Mac came out in August 1996, although by this time, Windows was getting 3.0        Dell Inspiron E1505 battery .

Version 2 was included in Windows 95 OSR 1 and Microsoft's Internet Starter Kit for Windows 95 in early 1996. It launched with twelve languages including English but this expanded to 24, 20, and 9 for Win 95, Win 3.1, and Mac respectively by April 1996. The 2.0i version supported double-byte character-set        Dell Latitude E6400 battery .

Internet Explorer 3 was released on August 13, 1996, and went on to be much more popular than its predecessors. Internet Explorer 3 was the first major browser with CSS support, although this support was only partial. It also introduced support for ActiveX controls, Java applets, inline multimedia, and the PICS system for content metadata  HP Pavilion dv6000 Battery .

Version 3 also came bundled with Internet Mail and News, NetMeeting, and an early version of the Windows Address Book, and was itself included with Windows 95 OSR 2. Version 3 proved to be the first more popular version of Internet Explorer, which brought with it increased scrutiny      SONY VAIO VGN-FZ Battery .

In the months following its release, a number of security and privacy vulnerabilities were found by researchers and hackers. This version of Internet Explorer was the first to have the 'blue e' logo. The Internet Explorer team consisted of roughly 100 people during the development of three months     SONY VAIO VGN-FZ18 Battery .

The first major IE security hole, the Princeton Word Macro Virus Loophole, was discovered on August 22, 1996 in IE3. Backwards compatibility was handled by allowing users who upgraded to IE3 to still use the last IE, because the installation converted the previous version to a separate directory     SONY VAIO VGN-FZ21E Battery .

Internet Explorer 4, released in September 1997, deepened the level of integration between the web browser and the underlying operating system. Installing version 4 on a Windows 95 or Windows NT 4 machine and choosing Windows Desktop Update would result in the traditional Windows Explorer being replaced by a version more akin to a web browser interface, as well as the Windows desktop itself being web-enabled via Active Desktop  SONY VAIO VGN-FW21E Battery .

The integration with Windows, however, was subject to numerous packaging criticisms (see United States v. Microsoft). This option was no longer available with the installers for later versions of Internet Explorer but was not removed from the system if already installed      SONY VAIO VGN-NR11S/S Battery .

Internet Explorer 4 introduced support for Group Policy, allowing companies to configure and lock down many aspects of the browser's configuration as well as support for offline browsing.Internet Mail and News was replaced with Outlook Express, and Microsoft Chat and an improved NetMeeting were also included      SONY VAIO VGN-NR11M/S Battery .

This version also was included with Windows 98. New features were added that allow you to save and retrieve posts in comment forms which are still not being used today. Internet Explorer 4.5 offered new features such as easier 128-bit encryption. It also offered a dramatic stability improvement over prior versions, particularly the 68k version which was especially prone to freezingSONY VAIO VGN-NR11Z/S Battery .

Internet Explorer 5, launched on March 18, 1999, and subsequently included with Windows 98 Second Edition and bundled with Office 2000, was another significant release that supported bi-directional text, ruby characters, XML, XSLT, and the ability to save web pages in MHTML format      SONY VAIO VGN-NR11Z/T Battery .

IE5 was bundled with Outlook Express 5. Also, with the release of Internet Explorer 5.0, Microsoft released the first version of XMLHttpRequest, giving birth to Ajax (even though the term "Ajax" wasn't coined until years later). It was the last with a 16-bit version     Sony VAIO VGN-FZ21E Battery .

Internet Explorer 5.01, a bug fix version, was released in December 1999. Windows 2000 includes this version. Internet Explorer 5.5 followed in July 2000, improving its print preview capabilities, CSS and HTML standards support, and developer APIs; this version was bundled withWindows Me     Sony VAIO VGN-FW21E Battery .

However, version 5 was the last version for Mac and UNIX. Version 5.5 was the last to have Compatibility Mode, which allowed Internet Explorer 4 to be run side by side with the 5.x. The IE team consisted of over 1,000 people by 1999, with funding on the order of 100 million USD per year    Sony VAIO VGN-NR11S/S Battery .

Internet Explorer 7 was released on October 18, 2006. It includes bug fixes, enhancements to its support for web standards, tabbed browsing with tab preview and management, a multiple-engine search box, a web feeds reader, Internationalized Domain Name support (IDN), Extended Validation Certificate support, and anti-phishing filter  Sony VAIO VGN-NR11Z/S Battery .

With IE7, Internet Explorer has been decoupled from the Windows Shell—unlike previous versions, the Internet Explorer ActiveX control is not hosted in the Windows Explorer process, but rather runs in a separate Internet Explorer process   Sony VAIO VGN-NR11M/S Battery .

It is included with Windows Vista and Windows Server 2008, and is available for Windows XP Service Pack 2 and later, and Windows Server 2003 Service Pack 1 and later. The original release of Internet Explorer 7 required the computer to pass a Windows Genuine Advantage validation check prior to installing, but on October 5, 2007, Microsoft removed this requirement Sony VAIO VGN-NR11Z/T Battery .

As some statistics show, by mid-2008, Internet Explorer 7 market share exceeded that of Internet Explorer 6 in a number of regions.

Internet Explorer 8 was released on March 19, 2009. It had been in development since August 2007 at the latest. On March 5, 2008, the first public beta (Beta 1) was released to the general public  SONY VAIO VGN-FZ180E Battery .

On August 27, 2008, the second public beta (Beta 2) was released. It is supported in Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista, Windows 7, and Windows Server 2008 on both 32-bit as well as 64-bit architectures. Internet Explorer 8 (IE8) RC1 was released on January 26, 2009      SONY VAIO VGN-FZ220E Battery .

Internet Explorer 8 "Final" was released on March 19, 2009. Security, ease of use, and improvements in RSS,CSS, and Ajax support are Microsoft's priorities for IE8. It includes much stricter compliance with web standards, including a planned full Cascading Style Sheets 2.1 compliance for the release version      SONY VAIO VGN-FZ340E Battery .

All these changes allow Internet Explorer 8 to pass the Acid2 test. However, to prevent compatibility issues, IE8 also includes the IE7 rendering behavior. Sites that expect IE7 quirks can disable IE8's breaking changes by including a meta element in the HEAD section of the HTML document         SONY VAIO VGN-FZ430E Battery .

IE8 also includes numerous improvements to JavaScript support as well as performance improvements,  although it still does not pass the Acid3 test, with version 8.0 scoring 20/100. It includes support for Accelerators—which allow supported web applications to be invoked without explicitly navigating to them—and WebSlices—which allows portions of page to be subscribed to and monitored from a redesigned Favorites Bar SONY VAIO VGN-FZ460E Battery .

Other features include InPrivate privacy features and SmartScreen phishing filter.

Internet Explorer 9, currently in development, will have complete or nearly complete support for all CSS 3 selectors including border-radius and many other properties       SONY VAIO VGN-FZ480E Battery ,

faster JavaScript, embedded ICC v2 or v4 color profiles, and hardware accelerated rendering using Direct2D and DirectWrite. Microsoft has confirmed that Web Open Font Format (WOFF) will also be supported. WOFF is "a strong favorite" for standardization by the Web Fonts Working Group of W3C      SONY VAIO VGN-FZ4000 Battery .

Microsoft has continued to downplay the importance of passing the Acid3 test, but speculation that IE9 would support the SVG W3C recommendation was ignited when Microsoft announced they had joined the SVG Working Group. Support for the HTML5 video and audio tags was also promised       SONY VAIO VGN-FZ31E Battery .

Some industry experts predict that Microsoft will release IE9 as a major out-of-band version that is not tied to any particular version of Windows. According to the Internet Explorer 9 Test Drive page, the system requirements for IE9 are Windows Vista SP2 (with Platform Upgrade and IE8) or Windows 7       SONY VAIO VGN-FZ31B Battery .

The final build of IE9 is expected to be released in 2011.

At MIX 10, the first IE9 Platform Preview was released, which featured support for CSS3 and SVG, a new JavaScript engine called Chakra, and a score of 55/100 on the Acid3 test (up from 20/100 for IE8)        SONY VAIO VGN-FZ31J Battery .

On May 5, 2010, the second IE9 Platform Preview was released, which featured a score of 68/100 on the Acid3 test and faster performance on the WebKit SunSpider JavaScript benchmark than the first IE9 Platform Preview. On June 23, 2010, the third IE9 Platform Preview was released         SONY VAIO VGN-FZ31M Battery ,

which scores 83/100 on the Acid3 test and introduced support for<audio>, <video>, and <canvas> elements and WOFF. On August 4, 2010, the fourth IE9 Platform Preview was released, which features a score of 95/100 on the Acid3 test and a faster JScript engine than the third IE9 Platform Preview          SONY VAIO VGN-FZ31Z Battery .

On August 12, 2010, Microsoft announced that the IE9 Public Beta would launch on September 15, 2010 at a special event in San Francisco linked to the idea of 'beauty of the web. It was also confirmed that the browser would only function with Windows Vista and Windows 7       SONY VAIO VGN-FZ38M Battery .

On September 15, 2010, Microsoft launched the IE9 Public Beta, alongside Platform Preview 5. The sixth IE9 Platform Preview was released on October 28, 2010, and includes support for CSS3 2D transforms and HTML5 semantic elements. The seventh IE9 Platform Preview was released on November 17, 2010, and features better JScript performance   SONY VGP-BPS8 Battery .

On February 10, 2011, the IE9 Release Candidate was released, featuring improved performance, a tracking protection feature, a refined UI, support for more web standards, and other improvements      SONY VGP-BPS13/S Battery .

Internet Explorer has been designed to view a broad range of web pages and to provide certain features within the operating system, including Microsoft Update. During the heyday of the browser wars, Internet Explorer superseded Netscape only when it caught up technologically to support the progressive features of the time      SONY VGP-BPS13A/B Battery .

Standards support

Internet Explorer, using the Trident layout engine:

  • supports HTML 4.01, CSS Level 1, XML 1.0, and DOM Level 1, with minor implementation gaps     SONY VGP-BPS13B/B Battery.
  • fully supports XSLT 1.0 as well as an obsolete Microsoft dialect of XSLT often referred to as WD-xsl, which was loosely based on the December 1998 W3C Working Draft of XSL. Support for XSLT 2.0 lies in the future: semi-official Microsoft bloggers have indicated that development is underway, but no dates have been announced       SONY VGP-BPS13A/S Battery .
  • partially supports CSS Level 2 and DOM Level 2, with major implementation gaps and conformance issues. Almost full conformance to CSS 2.1 has been added in the Internet Explorer 8 release.
  • supports XHTML in Internet Explorer 9 (Trident version 5.0). Prior versions can render XHTML documents authored with HTML compatibility principles and served with a text/html MIME-type       SONY VGP-BPS13AS Battery .
  • fully supports SVG in Internet Explorer 9 (Trident version 5.0).

Internet Explorer uses DOCTYPE sniffing to choose between standards mode and a "quirks mode" in which it deliberately mimicks nonstandard behaviors of old versions of MSIE for HTML and CSS rendering on screen (Internet Explorer always uses standards mode for printing). It also provides its own dialect ofECMAScript called JScript       Dell Inspiron 1320n Battery .

Internet Explorer had been subjected to criticism by W3C over its limited support for SVG promoted by W3C.

Non-standard extensions

Internet Explorer has introduced an array of proprietary extensions to many of the standards, including HTML, CSS, and the DOMDell Inspiron 1464 Battery .

This has resulted in a number of web pages that appear broken in standards-compliant web browsers and has introduced the need for a "quirks mode" to allow for rendering improper elements meant for Internet Explorer in these other browsers      Dell Inspiron 1564 Battery .

Internet Explorer has introduced a number of extensions to JScript that have been adopted by other browsers. These include the innerHTML property, which returns the HTML string within an element; the XMLHttpRequest object, which allows the sending of HTTP request and receiving of HTTP response        Dell Inspiron 1764 Battery ;

and the designMode attribute of the contentDocument object, which enables rich text editing of HTML documents. Some of these functionalities were not possible until the introduction of the W3C DOM methods. Its Ruby character extension to HTML is also accepted as a module in W3C XHTML 1.1, though it is not found in all versions of W3C HTML    Dell Studio 1450 Battery .

Microsoft submitted several other features of IE for consideration by the W3C for standardization. These include the 'behavior' CSS property, which connects the HTML elements with JScript behaviors (known as HTML Components, HTC)   Dell Studio 1457 Battery ;

HTML+TIME profile, which adds timing and media synchronization support to HTML documents (similar to the W3C XHTML+SMIL), and the VML vector graphicsfile format. However, all were rejected, at least in their original forms. VML was, however, subsequently combined with PGML (proposed by Adobe and Sun)      Dell Latitude D610 Battery ,

resulting in the W3C-approved SVG format, currently one of the few vector image formats being used on the web, and which IE is now virtually unique in not supporting.

Other non-standard behaviors include     Toshiba NB100 Battery :

support for vertical text, but in a syntax different from W3C CSS3 candidate recommendation, support for a variety of image effects  and page transitions, which are not found in W3C CSS, support for obfuscated script code, in particular JScript.Encode(). Support for embedding EOT fonts in web pages      Toshiba Satellite M65 battery .


The favicon (short for "favorites icon") introduced by Internet Explorer is now also supported and extended in other browsers. It allows web pages to specify a 16-by-16 pixel image for use in bookmarks       Toshiba Satellite M60 battery .

In IE, support was, and still is, provided only for the native Windows ICO format; in other browsers it has now been extended to other types of images such as PNG and GIF.

Usability and accessibility

The "quick tabs" feature available inInternet Explorer 8       Dell Latitude D830 Battery

Internet Explorer makes use of the accessibility framework provided in Windows. Internet Explorer is also a user interface for FTP, with operations similar to that of Windows Explorer. Pop-up blocking and tabbed browsing were added respectively in Internet Explorer 6 and Internet Explorer 7       Dell Latitude D620 Battery .

Tabbed browsing can also be added to older versions by installing MSN Search Toolbar or Yahoo Toolbar.


Internet Explorer caches visited content in the Temporary Internet Files folder to allow quicker access (or offline access) to previously visited pages       Dell Inspiron Mini 10 Battery .

The content is indexed in a database file, known as Index.dat. Multiple Index.dat files exist which index different content—visited content, web feeds, visitedURLs, cookies, etc.

Prior to IE7, clearing the cache used to clear the index but the files themselves were not reliably removed, posing a potential security and privacy risk        Sony VGN-FW11S Battery .

In IE7 and later, when the cache is cleared, the cache files are more reliably removed, and the index.dat file is overwritten with null bytes.

Group Policy

Internet Explorer is fully configurable using Group Policy       Sony VGN-FW11M Battery .

Administrators of Windows Server domains can apply and enforce a variety of settings that affect the user interface (such as disabling menu items and individual configuration options), as well as underlying security features such as downloading of files, zone configuration, per-site settings, ActiveX control behavior and others        Sony VGN-FW139E/H battery .

Policy settings can be configured for each user and for each machine. Internet Explorer also supports Integrated Windows Authentication.


The architecture of IE8. Previous versions had a similar architecture, except that both tabs and the UI were within the same process. Consequently, each browser window could have only one "tab process"       Dell Latitude E5400 Battery .

Internet Explorer uses a componentized architecture built on the Component Object Model (COM) technology. It consists of several major components, each of which is contained in a separate Dynamic-link library (DLL) and exposes a set of COM programming interfaces hosted by the Internet Explorer main executable, iexplore.exe:

  • WinInet.dll is the protocol handler for HTTP, HTTPS and FTP. It handles all network communication over these protocols.
  • URLMon.dll is responsible for MIME-type handling and download of web content, and provides a thread-safe wrapper around WinInet.dll and other protocol implementations      Dell Latitude E4200 Battery .
  • MSHTML.dll houses the Trident rendering engine introduced in Internet Explorer 4, which is responsible for displaying the pages on-screen and handling the Document Object Model of the web pages. MSHTML.dll parses the HTML/CSS file and creates the internal DOM tree representation of it        Dell Inspiron 300M Battery .
  • It also exposes a set of APIs for runtime inspection and modification of the DOM tree. The DOM tree is further processed by a layout engine which then renders the internal representation on screen.
  • IEFrame.dll contains the user interface and window of IE in Internet Explorer 7 and above  Dell Vostro A840 Battery .
  • ShDocVw.dll provides the navigation, local caching and history functionalities for the browser.
  • BrowseUI.dll is responsible for the browser user interface, including the browser chrome, which houses all the menus and toolbars       Dell Studio 1737 battery .

Internet Explorer does not include any native scripting functionality. Rather, MSHTML.dll exposes an API that permit a programmer to develop a scripting environment to be plugged-in and to access the DOM tree. Internet Explorer 8 includes the bindings for the Active Scripting engine        Dell Inspiron E1505 battery ,

which is a part ofMicrosoft Windows and allows any language implemented as an Active Scripting module to be used for client-side scripting. By default, only the JScript andVBScript modules are provided; third party implementations like ScreamingMonkey (for ECMAScript 4 support) can also be used            Dell RM791 battery .

Microsoft also makes available the Microsoft Silverlight runtime that allows CLI languages, including DLR-based dynamic languages like IronPython and IronRuby, to be used for client-side scripting.

Internet Explorer 8 introduces some major architectural changes, called Loosely Coupled IE (LCIE)  Dell XPS M1530 battery .

LCIE separates the main window process (frame process) from the processes hosting the different web applications in different tabs (tab processes). A frame process can create multiple tab processes, each of which can be of a different integrity level; each tab process can host multiple web sites        Dell XPS M2010 battery .

The processes use asynchronous Inter-Process Communication to synchronize themselves. Generally, there will be a single frame process for all web sites. In Windows Vista with Protected Mode turned on, however, opening privileged content (such as local HTML pages) will create a new tab process as it will not be constrained by Protected Mode     Acer Aspire One battery .


Internet Explorer exposes a set of Component Object Model (COM) interfaces that allow other components to extend the functionality of the browser. Extensibility is divided into two types: Browser extensibility and Content extensibility  Toshiba Satellite P10 Battery .

The browser extensibility interfaces can be used to plug in components to add context menu entries, toolbars, menu items or Browser Helper Objects (BHO). BHOs are used to extend the feature set of the browser, whereas the other extensibility options are used to expose the feature in the UI        SONY VGN-FZ210CE Battery .

Content extensibility interfaces are used by different content-type handlers to add support for non-native content formats.  BHOs not only have unrestricted access to the Internet Explorer DOM and event model, they also can access the filesystem, registry and other OS components        Dell Precision M70 Battery .

Content extensibility can be either in terms of Active Documents (Doc Objects) (e.g., SVG or MathML) or ActiveX controls.ActiveX controls are used for content handlers that render content embedded within an HTML page (e.g., Adobe Flash or Microsoft Silverlight)       Toshiba Satellite L305 Battery .

Doc objects are used when the content type won't be embedded in HTML (e.g., Microsoft Word, PDF orXPS). In fact, the Trident rendering engine is itself exposed as a Doc object, so HTML in itself is treated as an Active Document   Toshiba Satellite T4900 Battery .

Internet Explorer add-on components run with the same privileges as the browser itself, unlike client-side scripts that have a very limited set of privileges. Add-ons can be installed either locally, or directly by a web site. Since the add-ons have a more privileged access to the system, malicious add-ons can and have been used to compromise the security of the system   Toshiba PA3399U-2BRS battery .

Internet Explorer 6 Service Pack 2 onwards provide various safeguards against this, including an Add-onManager for controlling ActiveX controls and Browser Helper Objects and a "No Add-Ons" mode of operation as well as greater restrictions on sites installing add-ons   Toshiba Satellite A200 Battery .

Internet Explorer itself can be hosted by other applications via a set of COM interfaces. This can be used to embed the browser functionality inside the application. Also, the hosting application can choose to host only the MSHTML.dll rendering engine, rather than the entire browser       Toshiba Satellite 1200 Battery .


Internet Explorer uses a zone-based security framework that groups sites based on certain conditions, including whether it is an Internet- or intranet-based site as well as a user-editable whitelist. Security restrictions are applied per zone; all the sites in a zone are subject to the restrictions      Toshiba Satellite M300 Battery .

Internet Explorer 6 SP2 onwards uses the Attachment Execution Service of Microsoft Windows to mark executable files downloaded from the Internet as being potentially unsafe. Accessing files marked as such will prompt the user to make an explicit trust decision to execute the file, as executables originating from the Internet can be potentially unsafe      SONY VGP-BPS13A/Q Battery .

This helps in preventing accidental installation of malware.

Internet Explorer 7 introduced the phishing filter, that restricts access to phishing sites unless the user overrides the decision. With version 8, it also blocks access to sites known to host malware. Downloads are also checked to see if they are known to be malware-infected    SONY VGP-BPS13A/Q Battery .

In Windows Vista, Internet Explorer by default runs in what is called Protected Mode, where the privileges of the browser itself are severely restricted—it cannot make any system-wide changes. One can optionally turn this mode off but this is not recommendedSONY VGP-BPS13B/Q Battery .

This also effectively restricts the privileges of any add-ons. As a result, even if the browser or any add-on is compromised, the damage the security breach can cause is limited.

Patches and updates to the browser are released periodically and made available through the Windows Update service, as well as through Automatic Updates      SONY VGP-BPS13B/Q Battery .

Although security patches continue to be released for a range of platforms, most feature additions and security infrastructure improvements are only made available on operating systems which are in Microsoft's mainstream support phase  SONY VGP-BPS13/Q Battery .

On December 16, 2008, Trend Micro recommended users switch to rival browsers until an emergency IE patch was released to fix a potential security risk which "could allow outside users to take control of a person's computer and steal their passwords". Microsoft representatives countered this recommendation, claiming that "0.02% of internet sites" were affected by the flaw  SONY VGP-BPS13/Q Battery .

On December 17, 2008, a fix to the security problem above became available, with the release of the Security Update for Internet Explorer KB960714, which is available from Microsoft Windows Update's webpage. Microsoft has said that this update fixes the security risk found by Trend Micro the previous day      SONY VGP-BPS21A/B Battery .

Security vulnerabilities

Internet Explorer has been subjected to many security vulnerabilities and concerns: Much of the spyware, adware, and computer viruses across the Internet are made possible by exploitable bugs and flaws in the security architecture of Internet Explorer  SONY VGP-BPS21/S Battery ,

sometimes requiring nothing more than viewing of a malicious web page in order to install themselves. This is known as a "drive-by install". There are also attempts to trick the user into installing malicious software by misrepresenting the software's true purpose in the description section of an ActiveX security alert    SONY VGP-BPS21B Battery .

A number of security flaws affecting IE originated not in the browser itself, but ActiveX-based add-ons used by it. Because the add-ons have the same privilege as IE, the flaws can be as critical as browser flaws. This has led to the ActiveX-based architecture being criticized for being fault-prone         SONY VGP-BPS21A Battery .

By 2005, some experts maintained that the dangers of ActiveX have been overstated and there were safeguards in place. In 2006, new techniques using automated testing found more than a hundred vulnerabilities in standard Microsoft ActiveX components  SONY VGP-BPS21 Battery .

Security features introduced in then recently released Internet Explorer 7 mitigated some of these vulnerabilities.

Internet Explorer in 2008 had a number of published security vulnerabilities. According to research done by security research firm Secunia, Microsoft did not respond as quickly as its competitors in fixing security holes and making patches available  Sony VGP-BPS21A/B Battery .

The firm also reported 366 vulnerabilities in ActiveX controls, an increase from the prior year.

According to the latest information, Secunia reports that IE6 has 24 known unpatched vulnerabilities, IE7 has 11, and IE8 has 4. The most severe unpatched Secunia advisories affecting Microsoft Internet Explorer 6.x, 7.x, and 8     Sony VGP-BPS21/S Battery .

x with all vendor patches applied, are all rated Extremely critical. The oldest known unpatched vulnerabilities for IE6, IE7, and IE8 date from November 7, 2003, June 6, 2006, and February 26, 2007 respectively    Sony VGP-BPS21A Battery .

According to the latest information, security research firm SecurityFocus reports that IE6 has 396 known unpatched vulnerabilities, IE7 has 22, and IE8 has 25. The oldest known unpatched vulnerabilities for IE6, IE7, and IE8 date from November 20, 2000, May 17, 2007, and April 11, 2009 respectively   Sony VGP-BPS21 Battery .

Internet Explorer has been criticized by one Chris Evan for having a known security vulnerability which could allow information disclosure to remain unfixed for at least 600 days. Microsoft says that it had known about this vulnerability but it was of very low severity as the victim web site must be configured in a special way for this attack to be feasible at all  Sony Vaio PCG-5G2L Battery .

In December 2010, researchers have been able to bypass the "Protected Mode" feature in Internet Explorer.

Vulnerability exploited in attacks on U.S. firms

In an advisory on January 14, 2010, Microsoft said that attackers targeting Google and other U.S  Sony Vaio PCG-5G3L Battery .

companies used software that exploits a security hole, which had already been patched, in Internet Explorer. The vulnerability affected Internet Explorer 6, IE7, and IE8 on Windows 7, Vista, Windows XP, Server 2003, and Server 2008 R2, as well as IE 6 Service Pack 1 on Windows 2000 Service Pack 4   Sony Vaio PCG-5J1L Battery .

The German government warned users against using Internet Explorer and recommended switching to an alternative web browser, due to the major security hole described above that was exploited in Internet Explorer.  The Australian and French Government issued a similar warning a few days later       Sony Vaio PCG-5K2L Battery .

The first browser they recommended was Mozilla Firefox, followed by Google Chrome.

Market adoption and usage share

Source: Median values from world wide summary table.

Internet Explorer (43.8%)

Mozilla Firefox (29.7%; Usage by version number)  Sony Vaio PCG-5J2L Battery

Google Chrome (13.0%)

Safari (6.1%)

Opera (2.2%)

Mobile browsers (4.3%)         Sony Vaio PCG-5K1L Battery

See also: Usage share of web browsers

The adoption rate of Internet Explorer seems to be closely related to that of Microsoft Windows, as it is the default web browser that comes with Windows. Since the integration of Internet Explorer 2.0 with Windows 95 OSR 1 in 1996, and especially after version 4.0's release, the adoption was greatly accelerated     Sony Vaio PCG-6S2L Battery :

from below 20% in 1996 to about 40% in 1998 and over 80% in 2000.

A CNN article noted at the release of Internet Explorer 4: "Microsoft's Internet Explorer has made inroads and various estimates put its share of the browser market 30 to 35 percent from about 10 percent a year ago      Sony Vaio PCG-6S3L Battery .

"  By 2002, Internet Explorer had almost completely superseded its main rival Netscape and dominated the market with up to 95 percent market share.

After having fought and won the browser wars of the late 1990s, Internet Explorer gained almost total dominance of the browser market     Sony Vaio PCG-6V1L Battery .

Having attained a peak of about 95% during 2002 and 2003, its market share has since declined at a slow but steady pace. This is mainly due to the adoption of Mozilla Firefox, which statistics indicate is currently the most significant competition  Sony Vaio PCG-6W1L Battery .

Nevertheless, Internet Explorer remains the dominant web browser, with a global usage share of around 60% (though measurements vary). Usage is higher in Asia and lower in Europe.

Firefox 1.0 had surpassed Internet Explorer 5 in early 2005 with Firefox 1.0 at roughly 8 percent market share   Sony Vaio PCG-6W2L Battery .

An article notes at the release of Internet Explorer 7 in October 2006 that "IE6 had the lion's share of the browser market with 77.22%. Internet Explorer 7 had climbed to 3.18%, while Firefox 2.0 was at 0.69%."

Internet Explorer 7 was released at the same time as Firefox 2.0, and overtook Firefox 1.x by November 2006, at roughly 9% market share   Sony Vaio PCG-6W3L Battery .

Firefox 2.0 had overtaken 1.x by January 2007,  but IE7 did not surpass IE6 until December 2007.  By January 2008, their respective version market share stood at 43% IE7, 32% IE6, 16% FF2, 4% Safari 3 and both FF1.x and IE5 versions at less than half a percent     Sony Vaio PCG-7111L Battery .

Approximate usage over time based on various usage share counters averaged for the year overall, or for the fourth quarter, or for the last month in the year depending on availability of reference.

According to StarCounter, which tracks internet usage data, Internet Explorer's marketshare fell below 50% in September 2010  Sony Vaio PCG-7112L Battery .

Market share history overview by year and version

Approximate usage over time based on various usage share counters averaged for the year overall, or for the fourth quarter, or for the last month in the year depending on availability of reference  Sony Vaio PCG-7113L Battery .

Industry adoption

The ActiveX extension mechanism is used by many public websites and web applications, including eBay. Similarly, Browser Helper Objects are also used by many search enginecompanies and third parties for creating add-ons that access their services, such as search engine toolbars       Sony Vaio PCG-7133L Battery .

Because of the use of COM, it is possible to embed web-browsing functionality in third-party applications. Hence, there are a number of Internet Explorer shells, and a number of content-centric applications like RealPlayer also use Internet Explorer's web browsing module for viewing web pages within the applications       Sony Vaio PCG-7Z2L Battery .

OS compatibility

IE versions, over time, have had widely varying OS compatibility, ranging from being available for many platforms and several versions of Windows to only a few versions of Windows        Sony Vaio PCG-8Y1L Battery .

Many versions of IE had some support for an older OS but stopped getting updates. The increased growth of the Internet in the 1990s and 2000s means that current browsers with small market shares have more total users than the entire market early on   Sony Vaio PCG-8Y2L Battery .

For example, 90% market share in 1997 would be roughly 60 million  users, but by the start of 2007 90% market share  would equate to over 900 million users.  The result is that later versions of IE6 had many more users in total than all the early versions put together   Sony Vaio PCG-8Z1L Battery .

The release of IE7 at the end of 2006 resulted in a collapse of IE6 market share; by February 2007, market version share statistics showed IE6 at about 50% and IE7 at 29%. Regardless of the actual market share, the most compatible version (across operating systems) of IE was 5.x    Sony Vaio PCG-8Z2L Battery .

which had Mac OS 9 and Mac OS X, Unix, and most Windows versions available and supported for a short period in the late 1990s (although 4.x had a more unified codebase across versions). By 2007, IE had much narrower OS support, with the latest versions supporting only Windows XP Service Pack 2 and above       Sony VAIO PCG-5G2L Battery .

Internet Explorer 5.0, 5.5, 6.0, and 7.0 (Experimental) have also been unofficially ported to the Linux operating system from the project IEs4Linux.

* Internet Explorer 6 SP2 is only available as part of Windows XP SP2 or Windows Server 2003 SP1 or SP2  Sony VAIO PCG-5G3L Battery .
** The version of Internet Explorer included with Windows 95 varied by OSR release; 2.0 was included with OSR1, 3.0 was included with OSR2, and 4.0 was included with OSR2.5.
*** No native support, but possible with third-party "Standalone" installer    Sony VAIO PCG-5J1L Battery .
& Final version of Windows XP Service Pack 3 does not include IE7.
$ No native support, but possible with third party Standalone installer of IE6 Alpha. See also Internet Explorer Mobile. Non-desktop versions of IE have supported Windows CE also       Sony VAIO PCG-5K2L Battery .
£ Internet Explorer 2.0 and 2.0.1 requires System 7.0.1 or higher. Internet Explorer 2.1 requires System 7.1 or higher.
€ Included Internet Explorer 3.01 in Mac OS 8.1; Internet Explorer 4.01 in Mac OS 8.5 and 8.5.1; Internet Explorer 4.5 from Mac OS 8.6 to 9.0.4; Internet Explorer 5 from Mac OS 9.1 to 9.2.2       Sony VAIO PCG-5J2L Battery .
¥ Internet Explorer 5 Macintosh Edition requires Mac OS 7.6 or higher. Internet Explorer version 5.1; 5.1.4; 5.1.5; 5.1.6 and 5.1.7 requires Mac OS 8.0 or higher or Mac OS 7.6.1 with Appearance Manager.
16 16-bit version        Sony VAIO PCG-5K1L Battery

"Standalone" Internet Explorer

Early versions of Internet Explorer such as 5 had a compatibility mode to run Internet Explorer 4, though this feature was dropped (also, Internet Explorer for Mac users could still use 4.5 after installing IE 5)         Sony VAIO PCG-5L1L Battery .

While Microsoft claims it is impossible to keep multiple versions of Internet Explorer on the same machine, some hackers have successfully separated several versions of Internet Explorer, making them standalone applications. These are referred to as "standalone" IEs and have included versions 3 through 7     Sony VAIO PCG-6S2L Battery .

  • Multiple IEs in Windows Web Design—The web developer Joe Maddalone who found the solution.
  • Xenocode Browser Sandbox—Xenocode application virtualization.

Microsoft has discontinued standalone installers for Internet Explorer to the general public     Sony VAIO PCG-6S3L Battery .

However, there are unofficial procedures for downloading the complete install package. Internet Explorer standalone uses a feature introduced in Windows 2000 called DLL redirection to force it to load older DLLs than the ones installed on the system  Sony VAIO PCG-6W1L Battery .

  • IE Collection. An installer for the standalone versions of IE8.0, IE7.0, IE6.0, IE5.51, IE5.01, IE4.01, IE3.0, IE2.01, IE1.5, and IE1.0.
  • Microsoft Support document, with instructions for downloading the entire set of installation files.

It is also possible to install Internet Explorer via Wine   Sony VAIO PCG-6V1L Battery .

  • IEs4Linux automatically sets up Internet Explorer 5.0, 5.5, and 6.0 in Wine. Supporting Internet Explorer 7 is currently in development; as of August 2007, the IE7 rendering engine can be used with the IE6 user interface  Sony VAIO PCG-6W1L Battery .

After Internet Explorer 7 is installed, an Internet Explorer 6 executable is still available in C:\WINDOWS\ie7, hidden by default. Launching this executable provides the user with the older IE6 interface, however web pages are rendered using the IE7 engine. The IE6 engine can be re-enabled by placing a file named "iexplore.exe.local" into the IE7 folder  Sony VAIO PCG-6W2L Battery .

As an alternative to using IE standalone, Microsoft now makes available Microsoft Virtual PC images containing pre-activated copies of Windows XP with either IE 6 or IE 7 installed.  Microsoft recommends this approach for web developers seeking to test their pages in the different versions of IE as the standalone versions are unsupported and may not work the same way as a properly installed copy of IE   Sony VAIO PCG-6W3L Battery .


While a major upgrade of Internet Explorer can be uninstalled in a traditional way if the user has saved the original application files for installation, the matter of uninstalling the version of the browser that has shipped with an operating system remains a controversial one       Sony VAIO PCG-7111L Battery .

The idea of removing a stock install of Internet Explorer from a Windows system was proposed during the United States v. Microsoft case. One of Microsoft's arguments during the trial was that removing Internet Explorer from Windows may result in system instability       Sony VAIO PCG-7112L Battery .

Removing Internet Explorer does have a number of consequences. Applications that depend on libraries installed by IE will fail to function (or malfunction). The Windows help and support system will also not function due to the heavy reliance on HTML help files and components of IE       Sony VAIO PCG-7113L Battery .

In versions of Windows before Vista, it is also not possible to run Microsoft's Windows Update or Microsoft Updatewith any other browser due to the service's implementation of an ActiveX control, which no other browser supports. In Windows Vista, Windows Update is implemented as a Control Panel applet     Sony VAIO PCG-7Z1L Battery .

With Windows 7, Microsoft added the ability to safely remove Internet Explorer 8 from Windows. Microsoft does not allow the dependencies to be removed through this process, but the Internet Explorer executable (iexplore.exe) is removed without harming any other Windows components   Sony VAIO PCG-7Z2L Battery .

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16 février 2011 3 16 /02 /février /2011 11:41

Windows Mobile is a mobile operating system developed by Microsoft that was used in smartphones and mobile devices, but is being currently phased out to specialized markets. It is superseded by Windows Phone 7   (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk.

The current and last version is "Windows Mobile 6.5". It is based on the Windows CE 5.2 kernel, and features a suite of basic applications developed with the Microsoft Windows API. It is designed to be somewhat similar to desktop versions of Windows, feature-wise and aesthetically   Dell Studio XPS 1640 Battery .

Additionally, third-party software development is available for Windows Mobile, and software applications can be purchased via the Windows Marketplace for Mobile.

Originally appearing as the Pocket PC 2000 operating system, most Windows Mobile devices come with a stylus pen, which is used to enter commands by tapping it on the screen  Dell Vostro 1710 Battery .

Microsoft announced a completely new phone platform, Windows Phone 7, at the Mobile World Congress in Barcelona on February 15, 2010. Phones running Windows Mobile 6.x will not be upgradeable to version 7.

Windows Mobile's share of the smartphone market has fallen year-on-year, decreasing 20% in Q3 2009  Dell KM958 battery .

It is the 5th most popular smartphone operating system, with a 5% share of the worldwide smartphone market (after Symbian, BlackBerry OS, Android and iPhone).In the United States, it is the 3rd most popular smartphone operating system for business use (after BlackBerry OS and iPhone), with a 24% share among enterprise users   Dell Studio 1555 battery.

Microsoft is phasing out Windows Mobile to specialized markets, such as rugged devices, and focusing on its new mobile platform, Windows Phone 7.

Windows Mobile for Pocket PC carries these standard features in most of its versions   Sony VGP-BPS13 battery :

  • Today Screen shows the current date, owner information, upcoming appointments, e-mail messages, and tasks. (Is now Home screen in later WM6.5 builds)
  • The taskbar shows the current time and the volume   Sony VGP-BPS13/B battery .
  • Office Mobile a suite of Mobile versions of Microsoft Office applications
  • Outlook Mobile comes with Windows Mobile.
  • Internet Explorer Mobile is an Internet browser developed by Microsoft for Pocket PC and Handheld PC that comes loaded by default with Windows Mobile and Windows CE for Handheld PC    Sony VGP-BPS13/S battery .
  • Windows Media Player for Windows Mobile.
  • Client for PPTP VPNs.
  • Internet Connection Sharing (ICS) which in mobile phones allows attached computers to share internet connections via USB and Bluetooth      Sony VGP-BPS13A/B battery .
  • Coherent file system similar to that of Windows 9x/Windows NT and support for many of the same file types.
  • Ability to multitask.

There are three versions of Windows Mobile for various hardware devices      Sony VGP-BPS13B/B battery :

  • Windows Mobile Professional runs on (smartphones) with touchscreens
  • Windows Mobile Standard runs on phones with regular screens
  • Windows Mobile Classic which runs on 'Windows Mobile Classic devices' (Pocket PCs)   Sony VGP-BPL9 battery .

Windows Mobile Classic devices (Pocket PC)

A 'Windows Mobile Classic device' is a Windows Mobile personal digital assistant (PDA) that does not have telephone functionality. It was formerly known as the Pocket PC. It was the original intended platform for the Windows Mobile operating system  Sony VGP-BPS13B/B battery .

These devices consisted of both standalone Pocket PC devices without mobile phone capabilities, and those that included mobile phone capabilities. The most current name of Windows Mobile intended for use on Pocket PCs is officially "Windows Mobile 6 Professional"    Sony VGP-BPL15 battery

for devices with mobile phone capabilities and "Windows Mobile 6 Classic" for devices without mobile phone capabilities.

Windows Mobile Smartphones

The 'Windows Mobile' (Microsoft's term for its range of smartphones) became the next hardware platform after the Pocket PC to run Windows Mobile, and debuted with the release of Pocket PC 2002   Dell Inspiron E1505 battery .

Although in the broad sense of the term "Smartphone", both Pocket PC phones and Microsoft branded Smartphones each fit into this category, it should be noted that Microsoft's use of the term "Smartphone" includes only more specific hardware devices that differ from Pocket PC phones          Dell Latitude E6400 battery .

Such Smartphones were originally designed without touchscreens, intended to be operated more efficiently with only one hand, and typically had lower display resolution than Pocket PCs. Microsoft's focus for the Smartphone platform was to create a device that functioned well as a phone and data device in a more integrated manner       HP Pavilion dv6000 Battery .

Pocket PC 2000

Pocket PC 2000, originally codenamed "Rapier", was released on April 19, 2000, and was based on Windows CE 3.0. It was the debut of what was later dubbed the Windows Mobile operating system, and meant to be a successor to the operating system aboard Palm-Size PCs        SONY VAIO VGN-FZ Battery .

Backwards compatibility was retained with such Palm-Size PC applications. Pocket PC 2000 was intended mainly for Pocket PC devices, however several Palm-Size PC devices had the ability to be updated also. Further, several Pocket PC 2000 phones were released, however Microsoft's "Smartphone" hardware platform was not yet created   SONY VAIO VGN-FZ18 Battery .

The only resolution supported by this release was 240 x 320 (QVGA). Removable storage card formats that were supported were CompactFlash andMultiMediaCard. At this time Pocket PC devices had not been standardized with a specific CPU architecture. As a result, Pocket PC 2000 was released on multiple CPU architectures; SH-3, MIPS, and ARM   SONY VAIO VGN-FZ21E Battery .

Aesthetically, the original Pocket PC operating system was similar to Windows 98, Windows Me, and Windows 2000 operating systems.

Features/built-in applications for Pocket PC 2000 included the following       SONY VAIO VGN-FW21E Battery :

  • Pocket Office
  • Pocket Internet Explorer
  • Windows Media Player
  • Microsoft Reader
  • Microsoft Money
  • Notes, a written and sound note-taking application supported by most versions of Windows Mobile
  • Character recognition support          SONY VAIO VGN-NR11M/S Battery
  • Infrared (IR) File beaming capability

Pocket PC 2002

Pocket PC 2002, originally codenamed "Merlin", was released in October 2001. Like Pocket PC 2000, it was powered by Windows CE 3.0        SONY VAIO VGN-NR11Z/S Battery .

Although targeted mainly for 240 × 320 (QVGA) Pocket PC devices, Pocket PC 2002 was also used for Pocket PC phones, and for the first time, Smartphones. These Pocket PC 2002 Smartphones were mainly GSM devices        SONY VAIO VGN-NR11Z/T Battery .

With future releases, the Pocket PC and Smartphone lines would increasingly collide as the licensing terms were relaxed allowing OEMs to take advantage of more innovative, individual design ideas. Aesthetically, Pocket PC 2002 was meant to be similar in design to the then newly released Windows XP      Sony VAIO VGN-FZ21E Battery .

New features/built-in applications included the following:

  • Enhanced UI with theme support
  • Spell checker and Word count tool in Pocket Word
  • Savable downloads and WAP in Pocket Internet Explorer
  • Virtual Private Networking support        Sony VAIO VGN-FW21E Battery
  • Synchronization of folders
  • MSN Messenger
  • Terminal Services
  • Windows Media Player 8 with streaming capability       Sony VAIO VGN-NR11S/S Battery
  • Microsoft Reader 2
  • Palm OS support for file beaming
  • Improved Pocket Outlook
  • Digital rights management (DRM) support in Microsoft Reader        Sony VAIO VGN-NR11Z/S Battery

Windows Mobile 2003

Windows Mobile 2003 (aka wm2003 and WM2003), originally codenamed "Ozone",  was released on June 23, 2003, and was the first release under the Windows Mobile banner       Sony VAIO VGN-NR11M/S Battery .

It came in four editions: "Windows Mobile 2003 for Pocket PC Premium Edition", "Windows Mobile 2003 for Pocket PC Professional Edition", "Windows Mobile 2003 for Smartphone" and "Windows Mobile 2003 for Pocket PC Phone Edition". The last was designed especially for Pocket PCs which include phone functionalities. The Professional Edition was used in Pocket PC budget models  Sony VAIO VGN-NR11Z/T Battery .

It lacked a number of features that were in the Premium Edition, such as a client forL2TP/IPsec VPNs. Windows Mobile 2003 was powered by Windows CE 4.20.

New features/built-in applications included the following        SONY VAIO VGN-FZ180E Battery :

  • Support for add-on keyboards
  • Enhanced communications interface with Bluetooth device management
  • Bluetooth file beaming support
  • Bluetooth headset support         SONY VAIO VGN-FZ220E Battery
  • Pictures application with viewing, cropping, e-mail, and beaming support
  • Jawbreaker game
  • Enhanced Pocket Outlook with vCard and vCal support
  • Improved Pocket Internet Explorer          SONY VAIO VGN-FZ340E Battery
  • Windows Media Player 9.0 with streaming optimization
  • SMS reply options for Phone Edition
  • MIDI file support as ringtones in Phone Edition       SONY VAIO VGN-FZ430E Battery

Windows Mobile 2003 SE

Windows Mobile 2003 Second Edition, also known as "Windows Mobile 2003 SE", was released on March 24, 2004 and first offered on the Dell Axim x30. This was the last version which allowed users to backup and restore an entire device through ActiveSync  SONY VAIO VGN-FZ460E Battery .

New features/built-in applications included the following:

  • Portrait and Landscape switching for Pocket PCs
  • Single-Column layout in Pocket Internet Explorer       SONY VAIO VGN-FZ480E Battery
  • VGA (640×480), 176?220, 240x240, 480x480 Screen resolution
  • Wi-Fi Protected Access (WPA) support

Windows Mobile 5

Windows Mobile 5.0, originally codenamed "Magneto",was released at Microsoft's Mobile and Embedded Developers Conference 2005 in Las Vegas, May 9–May 12, 2005     SONY VAIO VGN-FZ4000 Battery .

Microsoft offered mainstream support for Windows Mobile 5 through October 12, 2010, and extended support through October 13, 2015. It was first offered on the Dell Axim x51. It used the .NET Compact Framework 1.0 SP3 — an environment for programs based on .NET      SONY VAIO VGN-FZ31E Battery .

  • Windows Mobile 5.0 included Microsoft Exchange Server "push" functionality improvements that worked with Exchange 2003 SP2. The "push" functionality also required vendor/device support With AKU2 software upgrades all WM 5.0 devices supported DirectPush       SONY VAIO VGN-FZ31B Battery .
  • WM 5.0 featured increased battery life due to Persistent storage capability. Previously up to 50% (enough for 72 hours of storage) of battery power was reserved just to maintain data in volatile RAM. This continued the trend of Windows-based devices moving from using RAM as their primary storage medium to the use of a combination of RAM and flash memory (in use, no distinction between the two is obvious to users)       SONY VAIO VGN-FZ31J Battery .
  • Programs and frequently accessed data run in RAM, while most storage is in the flash memory. The OS seamlessly moves data between the two as needed. Everything is backed up in the flash memory, so unlike prior devices, WM5 devices lose no data if power is lost       SONY VAIO VGN-FZ31M Battery .
  • With Windows Mobile 5.0, OS updates were released as Adaptation kit upgrades. AKU 3.5 is the most recent release for WM 5.0.

Further new features and built-in applications included:

  • New version of Office called "Office Mobile"
    • PowerPoint Mobile        SONY VAIO VGN-FZ31Z Battery
    • Graphing capability in Excel Mobile
    • Tables and graphics insertion in Word Mobile
  • Windows Media Player 10 Mobile
  • Photo Caller ID          SONY VAIO VGN-FZ38M Battery
  • DirectShow support
  • Picture and Video package, which converged the management of videos and pictures
  • Enhanced Bluetooth support
  • Global Positioning System (GPS) management interface         SONY VGP-BPS8 Battery
  • Default QWERTY keyboard-support
  • Error reporting facility similar to that present in desktop and server Windows systems
  • ActiveSync 4.2 with 15% increased synchronization speed        SONY VGP-BPS13/S Battery

Windows Mobile 6

Windows Mobile 6, formerly codenamed "Crossbow", was released on February 12, 2007  at the 3GSM World Congress 2007. It comes in three different versions: "Windows Mobile 6 Standard" for Smartphones (phones without touchscreens), "Windows Mobile 6 Professional" for Pocket PCs with phone functionality, and "Windows Mobile 6 Classic" for Pocket PCs without cellular radios  SONY VGP-BPS13A/B Battery .

Windows Mobile 6 is powered by Windows CE 5.0 (version 5.2) and is strongly linked to Windows Live and Exchange 2007 products. Windows Mobile 6 Standard was first offered on the Orange's SPV E650, while Windows Mobile 6 Professional was first offered on the O2's Xda Terra        SONY VGP-BPS13B/B Battery .

Aesthetically, Windows Mobile 6 was meant to be similar in design to the then newly released Windows Vista. Functionally, it works much like Windows Mobile 5, but with much better stability.

New features/built-in applications include the following       SONY VGP-BPS13A/S Battery :

  • 320x320 and 800x480 (WVGA) screen resolution support (The S01SH or "Em One" by Sharp was the first and only device to have a 800x480 screen on WM5)
  • Office Mobile support for Smartphones
  • Operating System Live Update   SONY VGP-BPS13AS Battery
  • Improved Remote Desktop access  (Available for only certain Pocket PCs)
  • VoIP (Internet calling) support with AEC (Acoustic Echo Cancelling) and MSRT  Audio Codec
  • Windows Live for Windows Mobile
  • Customer Feedback option       Dell Inspiron 1320n Battery
  • Enhanced Microsoft Bluetooth Stack
  • Storage Card Encryption (encryption keys are lost if device is cold-booted).
  • Smartfilter for searching within programs
  • Improved Internet Sharing
  • HTML email support in Outlook Mobile         Dell Inspiron 1464 Battery
  • Search ability for contacts in an Exchange Server Address Book
  • AJAX, JavaScript, and XMLDOM support on Internet Explorer Mobile
  • Out of Office Replies with Microsoft Exchange 2007
  • Unlicensed Mobile Access (UMA) support for select operators
  • Server Search on Microsoft Exchange 2007         Dell Inspiron 1564 Battery
  • .NET Compact Framework v2 SP2 Preinstalled in ROM
  • Microsoft SQL Server 2005 Compact Edition Preinstalled in ROM
  • OneNote Mobile as a companion to Microsoft Office OneNote
  • Office Mobile 6.1 announced  with support for Office 2007 document formats (pptx, docx, xlsx)  Dell Inspiron 1764 Battery .

Windows Mobile 6.1

Windows Mobile 6.1 was announced April 1, 2008. It is a minor upgrade to the existing Windows Mobile 6 platform which brings with it various performance enhancements, a redesigned Home screen featuring horizontal tiles that expand on clicking to display more information, although this new home screen is featured only on Windows Mobile Standard edition  Dell Studio 1450 Battery .

This feature was inexplicably left out of the Professional edition. Several other changes such as threaded SMS, full page zooming in Internet Explorer and 'Domain Enroll' have also been added, along with a "mobile" version of the Microsoft OneNote program and an interactive "Getting Started" wizard      Dell Studio 1457 Battery .

Domain Enroll is functionality to connect the device to System Center Mobile Device Manager 2008, a product to manage mobile devices. There are other differences also. The most obvious for users is that the Standard version (like prior versions) still creates automatic links for telephone numbers in Tasks and Appointments     Dell Latitude D610 Battery ,

which allows for the easier click and dial of stored telephone numbers within these Outlook items. For some reason, the Professional version has eliminated this important feature. Windows Mobile 6.1 also featured improved bandwidth efficiency in its push-email protocol "Activesync" of "up to 40%",  this reduced data usage was the cause of considerably improved battery life in many devices  Toshiba NB100 Battery .

Aside from the visual and feature distinctions, the underlying CE versions can be used to differentiate WM6.0 from WM 6.1. The version of Windows CE in WM 6.0 is 5.2.*, with the final number being a 4 digit build ID (e.g. 5.2.1622 on HTC Wing). In WM 6.1, the CE version is 5.2.* with a 5 digit build number (e.g. 5.2.19216 on Palm Treo 800w)  Toshiba Satellite M65 battery .

Windows Mobile 6.5

Windows Mobile 6.5 was never part of Microsoft's mobile phone roadmap, and has been described by its chief executive, Steve Ballmer, as "not the full release [Microsoft] wanted" until the multi-touch enabled Windows Mobile 7 (now replaced by Windows Phone 7) arrived in 2010     Toshiba Satellite M60 battery .

Version 6.5 is an upgrade to Windows Mobile 6.1 that was released to manufacturers on May 11, 2009, and the first devices running the operating system debuted in late October '09. This incremental update includes some significant new added features, such as a revamped GUI, new today screen with vertically scrollable labels (called 'Titanium')     Dell Latitude D830 Battery ;

though is generally regarded as a minor upgrade. It also includes the new Internet Explorer Mobile 6 browser, which has an improved interface over prior versions.

Microsoft unveiled this version at the 2009 Mobile World Congress in February, and several devices now run this Windows Mobile version,those devices running Windows Mobile 6.5 onwards are marketed as "Windows phones"     Dell Latitude D620 Battery .

Along with Windows Mobile 6.5, Microsoft announced several Cloud computing services codenamed "SkyBox","SkyLine","SkyMarket".  "SkyBox" has been confirmed as My Phone, while "SkyMarket" has been confirmed as Windows Marketplace for Mobile      Dell Inspiron Mini 10 Battery .

Some aspects of the user interface have been redesigned with the home screen resembling that of Microsoft's Zune player and the sliding panel interface of Windows Mobile 6.1 Standard. This version was designed mainly for easier finger usage. Whilst this version of Windows Mobile does not natively support capacitive screens       Sony VGN-FW11S Battery ,

mobile manufacturers have been able to successfully implement it on their devices

Several phones currently running Windows Mobile 6.1 are updatable to Windows Mobile 6.5       Sony VGN-FW11M Battery .

Windows Mobile 6.5.1

Builds of Windows Mobile 6.5.1 have been unofficially ported to several Windows Mobile phones. Windows Mobile 6.5.1 brings a more finger-friendly user interface, including icon based soft buttons (rather than text based), an updated contacts app, Microsoft (rather than the mobile carrier) support for A-GPS, improved threaded text messaging,  and performance improvements  Sony VGN-FW139E/H battery .

Windows Mobile 6.5.

On February 2, 2010, the Sony Ericsson Aspen with Windows Mobile 6.5.3 was officially announced, making it the first Windows Phone 6.5.3 smartphone.Since November 2009, several 6.5.3 builds had leaked (28nnn) and had been unofficially ported to some Windows Phones    Dell Latitude E5400 Battery .

Windows Mobile 6.5.3 brings a more finger-friendly user interface with several new ease of use features such as support for multitouch, complete touch control i.e. no need for a stylus, and drag and drop start menu icons. Touchable tiles now replace soft keys       Dell Latitude E4200 Battery ."

Internet Explorer Mobile 6 has also received some major updates including decreased page load time, improved memory management and gesture smoothing.

Additional features of newer Windows Mobile 6.5.3 builds include threaded email and Office Mobile 2010      Dell Inspiron 300M Battery .

Windows Mobile 6.5.5

Several builds of Windows Mobile 6.5.x have leaked since January 2010 and have been unofficially ported to some Windows Mobile phones. The name Windows Mobile 6.5.5 has been applied to these newer builds. However, this naming scheme remains unconfirmed by Microsoft     Dell Vostro A840 Battery .

Windows Phone 7

Windows Phone 7 was launched in Europe, Singapore and Australia on October 21, 2010, and in the US & Canada on November 8, 2010, with the rest of the world to follow in 2011       Dell Studio 1737 battery .

Microsoft had originally planned to continue the Windows Mobile line to Windows Mobile 7, based on an upgrade to the Windows Mobile platform, codenamed Photon. The original Photon and Windows Mobile 7 have since been scrapped; however, Microsoft decided to create a new mobile OS platform and officially announced Windows Phone 7 Series in its place  Dell Inspiron E1505 battery .

Microsoft has since renamed the operating system from Windows Phone 7 Series to Windows Phone 7.

Windows Phone 7 was initially intended to be released during 2009, but several delays, likely due to the move away from Photon and to building an entirely different and new platform, prompted Microsoft to develop Windows Mobile 6.5 as an interim release  Dell RM791 battery .

During the Mobile World Congress 2010 in Barcelona, Microsoft revealed details of Windows Phone 7, which features a new operating system and integration with Xbox Live and Zune services.

Most phones currently running Windows Mobile 6.x are not upgradeable to Windows Phone 7,  although hacked firmwares with Phone 7 are becoming increasingly popular         Dell XPS M1530 battery .

Microsoft Kin

Microsoft Kin was a family of mobile telephones which started with Microsoft's purchase of Danger Hiptop in 2008. Microsoft Kin was developed inside Microsoft's Premium Mobile Experiences (PMX) division. Microsoft brought in employees from Danger Inc., with the intention of infusing industry talent and mobile experience into the project      Dell XPS M2010 battery .

The goal was said to be to create a mobile platform far superior to that of the Danger Sidekick. Reports say that Microsoft Kin was originally going to be based on Windows Phone 7. However, due to delays with the latter, it was built directly upon Windows CE. It featured the Zune marketplace, and used XNA as a game platform      Acer Aspire One battery .

The platform was aimed at producing phones designed for users who are heavily into social networking and instant messaging. The technology acquired from Danger Hiptop has been described as a family of mobile devices running a bespoke operating system as part of a client–server system that is then licenced to mobile carriers         Toshiba Satellite P10 Battery .

Microsoft introduced two new handsets based on Microsoft Kin, codenamed Turtle and Pure, possibly to debut at the Consumer Electronics Show. The Microsoft designed phones were manufactured by Sharp and co-branded.

The devices received very critical reviews and Microsoft announced the discontinuation of the KIN line on June 30, 2010, only six weeks after it was launched        SONY VGN-FZ210CE Battery .

Naming conventions

Other: Windows Mobile for Automotive 1.0, Windows Mobile software for Portable Media Centers


A Ford Territory with Windows Mobile advertising seen in Auckland, New Zealand in 2008      Dell Precision M70 Battery .

Windows Mobile's share of the smartphone market has been in decline year-on-year. Gartner research data showed that while the total smartphone industry grew 27% between 2008 and 2009, Windows Mobile's share of the smartphone market fell 2.7% in that same period     Toshiba Satellite L305 Battery .

In 2004, Windows Mobile accounted for 23% of worldwide smartphone sales.Windows Mobile was projected to overtake Symbian to become the leading mobile OS by 2010. But by 2008, its share had dropped to 14%. Microsoft licensed Windows Mobile to four out of the world's five largest mobile phone manufacturers, with Nokia being the exception     Toshiba Satellite T4900 Battery .

Although Microsoft apparently has 50 handset partners, 80% of the 50 million Windows Mobile devices made have been built by one contract manufacturing group, HTC, which makes handsets for several major companies under their brands, and under its own brandToshiba PA3399U-2BRS battery .

In February 2009 Microsoft signed a deal with the third largest mobile phone maker, LG Electronics, to license Windows Mobile OS on 50 upcoming LG smartphone models. But in September, 2009, Palm, Inc. announced it would drop Windows Mobile from its smartphone line-up      Toshiba Satellite A200 Battery .

An October 2009 report in DigiTimes said that Acer will shift its focus from Windows Mobile to Google Android.

At one time Windows Mobile was the most popular handset for business use, but by 2009 this was no longer the case  Toshiba Satellite 1200 Battery .

An InformationWeek survey found that 24% of planned business deployments of mobile application were for Windows Mobile, putting it in 3rd place, behind Blackberry (61%) and iPhone (27%).

In October 2009 Gartner predicted that by 2012 Windows Mobile would remain the fourth most popular smartphone platform during the rise of Android only due to BlackBerry falling from second to fifth    Toshiba Satellite M300 Battery .

The New York Times said that cellular telephone manufacturers were moving away from Windows Mobile, and instead shifting towards Android and Microsoft's new mobile platform, Windows Phone 7. Taiwan's Intelligence & Consulting Institute (MIC) predicted that Android's popularity might force Microsoft to reduce the Windows Mobile licensing fees it charges handset makers, in order to reduce further market share losses      SONY VGP-BPS13A/Q Battery .

Windows Mobile's loss of market share accelerated in the third quarter of 2009; it suffered a 20% drop compared to the prior quarter, at a time when total smartphone sales rose by 13%. Gartner estimated that by this time Windows Mobile's share of worldwide smartphone sales was 7.9%      SONY VGP-BPS13A/Q Battery .

Samsung announced in November 2009 that it would phase out the Windows Mobile platform,  to concentrate on its own Bada operating system, Google's Android, and Microsoft's Windows Phone 7      SONY VGP-BPS13B/Q Battery .

Possible trends

In late 2009, many industry analysts and media reports began to express concerns about the future viability of the Windows Mobile platform, and whether Microsoft will keep supporting it into the future         SONY VGP-BPS13B/Q Battery .

ZDnet said that "for all practical purposes, Windows Mobile is a dead platform", while CNET said "Windows Mobile has now been relegated resolutely to has-been status. "

ABI Research said: "Heading into 2010, the momentum (for Windows Mobile) has dissipated     SONY VGP-BPS13/Q Battery ."

Gartner analysts questioned whether Windows Mobile had a future beyond version 7, due to its poor performance and falling market share. However, Gartner said that while Windows Mobile may be discontinued for consumer-focused smartphones, it still had a future in specialized industrial applications, such as for ruggedized devices used in warehousing and delivery trucks  SONY VGP-BPS13/Q Battery .

Gartner said thatWindows Mobile 7 could be "the last throw of the dice."

Analysts J.Gold Associates said in BusinessWeek that Microsoft will likely exit the mobile operating system market sometime between 2010 and 2011, saying "There are better ways for Microsoft to make money from smartphones than to keep investing in a mobile operating system that's losing share and relevance      SONY VGP-BPS21A/B Battery ."

The New York Times reported that Windows Mobile "is foundering", as cellphone makers desert it in favor of Google's Android phone platform. It cited the difficulties in Microsoft's business model, which involves charging handset manufacturers up to $25 for each copy of Windows Mobile, while rival Google gives away Android for free     SONY VGP-BPS21/S Battery .

The Washington Post said Windows Mobile is "bleeding market share in the space, and the future looks grim." It said that Google is using Android to "kill" Windows Mobile.

In February 2010 Microsoft announced a new mobile operating system platform: Windows Phone 7     SONY VGP-BPS21B Battery .

It has been built from scratch and bears no resemblance to its predecessors. It was released on October 21, 2010 in Europe and on November 8, 2010 in the United States.

Software development

Third-party software development is available for the Windows Mobile operating system      SONY VGP-BPS21A Battery .

Developers have several options for deploying mobile applications. These include writing native code with Visual C++, writing Managed code that works with the .NET Compact Framework, or server-side code that can be deployed using Internet Explorer Mobile or a mobile client on a user's device       SONY VGP-BPS21 Battery .

The .NET Compact Framework is actually a subset of the .NET Framework and hence shares many components with software development on desktop clients, application servers, and web servers which have the .NET Framework installed, thus integrating networked computing space (a.k.a. "The Cloud")     Sony VGP-BPS21A/B Battery .

Microsoft typically releases Windows Phone software development kits (SDKs) that work in conjunction with their Visual Studio development environment. These SDKs include emulator images for developers to test and debug their applications while writing them     Sony VGP-BPS21/S Battery .

Microsoft also distributes Visual Studio 2008 / 2005 Professional Editions, and server / database counterparts to students as downloads free of charge via its DreamSpark program.

Developer communities have used the SDK to port later versions of Windows Mobile OS to older devices and making the OS images available for free, thus providing the devices with the current feature set     Sony VGP-BPS21A Battery .

Microsoft has tolerated this procedure for some time but decided in February 2007 to ask developers to take their OS images off the net, which in turn raised discussions. At the same time Microsoft offered upgrades to Windows Mobile 6 versions to manufacturers for free      Sony VGP-BPS21 Battery .

Lazarus, Lexico, NS Basic and Basic4ppc provide alternative development environments. They allow development on a separate computer, which is then downloaded to the target device. NS Basic and Basic4ppc allow development on the target device  Sony Vaio PCG-5G2L Battery .

Some 3rd party development tools such as Basic4ppc use the .NET Compact Framework. This has been possible only for the last couple years. Prior to the release of Windows Mobile 2003, third-party software was developed using Microsoft's eMbedded Visual Tools, eMbedded Visual Basic (eVB) and eMbedded Visual C (eVC)       Sony Vaio PCG-5G3L Battery .

eVB programs can usually be converted fairly easily to NS Basic/CE. or to Basic4ppc.

There is also a GCC port called CeGCC. For scripting languages, there is a Python port named PythonCE, and a Tcl-Tk port called eTcl. It can be used to develop applications on Windows Mobile phone     Sony Vaio PCG-5J1L Battery .

Satellite Forms is a rapid application development (RAD) tool that can produce Windows Phone compatible applications that use an RDK runtime engine. Extension libraries extend the functionality for various hardware.

On 5 July 2009, Microsoft opened a third-party application distribution service called Windows Marketplace for Mobile  Sony Vaio PCG-5K2L Battery .


  • Versions of Windows Mobile prior to 6.5.3 did not recognize multi-touch screens. Device maker HTC Corporation created some work-arounds to allow multi-touch to work on some applications it installed on its HD2 handset       Sony Vaio PCG-5J2L Battery .
  • However, Microsoft applications on this handset, such as the Internet Explorer web browser, do not support multi-touch.
  • Windows Mobile does not allow users to view file properties from File Explorer and so a third-party file explorer is needed to remove the "read-only" or "Hidden File" attributes applied to files. Hidden files can be viewed  Sony Vaio PCG-5K1L Battery .
  • Windows Mobile does not allow users to view file extensions of unknown file types, although third-party software is available to do this.
  • Windows Mobile devices can easily be used and reset by unauthorised users, such as thieves   Sony Vaio PCG-6S2L Battery ,
  • as the "Clear Storage" command can be invoked without the need for a password so long as the keypad is not locked and the phone is not turned off, because the CLEAR STORAGE is applied by using embedded, unmodifiable key sequence of "1234" which is also visibly shown in the phone     Sony Vaio PCG-6S3L Battery .
  • The interface of Windows Mobile 6.5 shows jarring inconsistencies, with some applications requiring users to hold a stylus to operate them.
  • Many Windows Mobile business applications were designed for a stylus-pen input, and are difficult or impossible to use on a capacitative multi-touch screen       Sony Vaio PCG-6V1L Battery .
  • Unlike Windows for desktop computers, the Windows Mobile operating system cannot be upgraded by users. Upgrades can only be supplied by telephone service providers or hardware providers          Sony Vaio PCG-6W1L Battery .
  • As this requires considerable resource to produce a custom upgrade for each device, generates no income (upgrades have not been chargeable), and extends the life of older equipment instead of encouraging purchase of new, Windows Mobile upgrades are rarely released       Sony Vaio PCG-6W2L Battery .
  • However, expert users have developed unofficial, sometimes modified, firmware; this unofficial firmware, or newer Windows Mobile or Phone firmware intended for other devices with the risk of possible incompatibility, can be installed if available with flashing software     Sony Vaio PCG-6W3L Battery .
  • Several analysts from both Gartner and J.Gold Associates have expressed concern about the long-term future of Windows Mobile. Motorola and Fedex said that Microsoft had given a commitment to continue supporting Windows Mobile, at least for use in rugged industrial devices       Sony Vaio PCG-7111L Battery .
  • On 25 September 2009, Microsoft CEO Steve Ballmer indicated that the company "screwed up with Windows Mobile". He lamented that Windows Mobile version 7 was not yet available. He said he had recently changed the Windows Mobile team to try to recoup losses     Sony Vaio PCG-7112L Battery .
  • Windows Mobile 6.5.x was based on the Windows CE 5.2 kernel, the same kernel that was running in Windows Mobile 5.0 in 2004. Windows Mobile 6.5.x has not been optimized for more modern processors, such as the Snapdragon processors. Its successor, Windows Phone 7, runs an updated kernel based on Windows CE 6 R3 and Windows CE 7  Sony Vaio PCG-7113L Battery .
  • A 2009 survey by CFI Group showed that Windows Mobile users had a low level of customer satisfaction when compared to users of other smartphones. Out of a possible 100 points, Windows Mobile rated only 66, compared with BlackBerry (73), Palm Pre (77), Google Android (77), and iPhone (83)      Sony Vaio PCG-7133L Battery .

Windows Phone 7 is a mobile operating system developed by Microsoft, and is the successor to its Windows Mobile platform. It is aimed at the consumer market instead of the enterprise market like its predecessor      Sony Vaio PCG-7Z2L Battery .

It launched in Europe, Singapore and Australia on October 21, 2010, and in the US and Canada on November 8, 2010, Mexico on November 24, 2010, with Asia to follow in 2011. With Windows Phone 7, Microsoft offers a new user interface with its design language named Metro      Sony Vaio PCG-8Y1L Battery ,

integrates the operating system with 3rd party and other Microsoft services, and plans to strictly control which hardware it runs on.

Microsoft unveiled Windows Phone 7 on February 15, 2010, at Mobile World Congress 2010 in Barcelona and revealed additional details at MIX 2010on March 15, 2010. The final SDK was made available on September 16, 2010  Sony Vaio PCG-8Y2L Battery .

Operating system development

Work on a major Windows Mobile update may have begun as early as 2004 under the codename "Photon", but work moved slowly and the project was ultimately cancelled        Sony Vaio PCG-8Z1L Battery .

In 2008, Microsoft reorganized the Windows Mobile group and started work on a new mobile operating system. The product was to be released in 2009 as Windows Phone, but several delays prompted Microsoft to develop Windows Mobile 6.5 as an interim release  Sony Vaio PCG-8Z2L Battery .

Windows Phone 7 was developed quickly. One result was that Windows Mobile applications do not run on it. Larry Lieberman, senior product manager for Microsoft’s Mobile Developer Experience, told eWeek: "If we’d had more time and resources, we may have been able to do something in terms of backward compatibility     Sony VAIO PCG-5G2L Battery ."

Lieberman said that Microsoft was attempting to look at the mobile phone market in a new way, with the end user in mind as well as the enterprise network. Terry Myerson, corporate VP of Windows Phone engineering, said, "With the move to capacitive touch screens, away from the stylus         Sony VAIO PCG-5G3L Battery ,

and the moves to some of the hardware choices we made for the Windows Phone 7 experience, we had to break application compatibility with Windows Mobile 6.5."


Windows Phone 7 is a rebranding of Microsoft’s old mobile OS called Windows Mobile. Before the official announcement of Windows Phone 7, Microsoft began to refer to devices running Windows Mobile as “Windows Phones”   Sony VAIO PCG-5J1L Battery .

Microsoft at first announced its new platform as "Windows Phone 7 Series" which initially came under criticism as being too wordy and difficult to say casually. Responding to this, on April 2, 2010 Microsoft announced that the "Series" would be dropped from the name, leaving the platform named Windows Phone 7        Sony VAIO PCG-5K2L Battery .

Microsoft's official statement on the matter was:

"Customers want a simpler way to say and use the name consistently. The important thing is keeping the focus on the Windows Phone brand, which we introduced in October and will continue investing in through Windows Phone 7 and beyond  Sony VAIO PCG-5J2L Battery ."


In February 2010, a Microsoft press release listed the companies that would help make and operate Windows Phone 7. Many hardware makers were listed in the release      Sony VAIO PCG-5K1L Battery .

HP later decided not to build devices for Windows Phone 7, citing that it wanted to focus on devices for its newly purchased WebOS.

Windows Phone 7 supports five languages: English, French, Italian, German and Spanish. Windows Phone Marketplace allows buying and selling applications in 17 countries and regions       Sony VAIO PCG-5L1L Battery :

Australia, Austria, Belgium, Canada, France, Germany, Hong Kong, India, Ireland, Italy, Mexico, New Zealand, Singapore, Spain, Switzerland, Puerto Rico, United Kingdom, and United States.

Windows Phone 7 was released in Europe on October 21, in North America on November 8, and in Mexico on November 24, 2010. A release in Asian countries will follow in 2011     Sony VAIO PCG-6S2L Battery .

On October 11, 2010, Microsoft's CEO Steve Ballmer announced 10 devices operating Windows Phone 7, made by HTC, Dell, Samsung, and LG, with sales beginning on October 21, 2010 in Europe and Australia and November 8, 2010 in the United States. The devices were available on 60 carriers in 30 countries, with additional devices to be launched in 2011     Sony VAIO PCG-6S3L Battery .

Microsoft reported on December 21, 2010 that in the first 6 weeks phone manufacturers sold 1.5 million Windows Phone 7 devices to mobile operators and retailers. On January 26, 2011 Microsoft stated that in the 4th quarter of 2010 it had sold more than 2 million Windows Phone 7 licenses for phones, which manufacturers had delivered to mobile operators and retailers   Sony VAIO PCG-6V1L Battery.

In January 2011, LG reported about its own handsets: "From an industry perspective we had a high expectation, but from a consumer point of view the visibility is less than we expected". At CEBIT Preview, Deutsche Telekom told Yahoo that its Windows Phone 7 handsets are selling better than expected       Sony VAIO PCG-6W1L Battery .

According to NPD Group, a group specialized in films, movies, and video games , Windows Phone 7 achieved a market-share of 2% among smartphones sold to consumers in the United States, 2 months after release, in the 4th quarter of 2010. On February 2, 2011, T-Mobile USA said of Windows Phone 7        Sony VAIO PCG-6W2L Battery :

"The customers are very satisfied with the experience. We’ve done well with the devices that we sold.”

Partnership with Nokia

On 11 February 2011, at a press event in London, Microsoft CED Steve Ballmer and Nokia CEO Stephen Elop announced a partnership between their companies in which Windows Phone 7 would become the primary smartphone operating system for Nokia  Sony VAIO PCG-6W3L Battery .

The event was largely focused on creating “a new global mobile ecosystem”, suggesting competition with Android and iOS by saying "It is now a three horse race". Integration of Microsoft services with Nokia’s own services were announced specifically that Bing would power search across Nokia devices         Sony VAIO PCG-7111L Battery ,

and an integration of Nokia Maps with Bing Maps as well as Nokia’s application store being integrated with the Windows Phone Marketplace .

]User interface

Windows Phone features a new user interface, based upon Microsoft's Windows Phone 7 design system, codenamed Metro   Sony VAIO PCG-7112L Battery .

The home screen, called the "Start screen", is made up of "Tiles". Tiles are links to applications, features, functions and individual items (such as contacts, web pages, applications or media items). Users can add, rearrange, or remove Tiles        Sony VAIO PCG-7113L Battery .

Tiles are dynamic and update in real time - for example, the tile for an email account would display the number of unread messages or a Tile could display a live update of the weather.

Several features of Windows Phone 7 are organized into "hubs", which combine local and online content via Windows Phone 7's integration with popular social networks such as Facebook andWindows Live     Sony VAIO PCG-7Z1L Battery .

For example, the Pictures hub shows photos captured with the device's camera and the user's Facebook photo albums, and the People hub shows contacts aggregated from multiple sources including Windows Live, Facebook, and Gmail. From the Hub, users can directly comment and 'like' on social network updates    Sony VAIO PCG-7Z2L Battery .

The other built-in hubs are Music and Video (which integrates with Zune), Games (which integrates with Xbox Live), Windows Phone Marketplace, and Microsoft Office.

Windows Phone 7 uses multi-touch technology   Sony VAIO PCG-8Y1L Battery .

The default Windows Phone 7 user interface has a dark theme that prolongs battery life on OLED screens as fully black pixels don't emit light. The user may choose a light theme instead, and can also choose from several accent colors.  User interface elements such as tiles are shown in the user's chosen accent color       WD passport essential (500GB/640GB) .

Third-party applications can be automatically themed with these colors.

Text input

Users input text by using an on-screen virtual keyboard, which has a dedicated key for inserting emoticons. Spell checking  and word prediction , and users may change a word after it has been typed by tapping the word,which will invoke a list of similar words  WD passport essential (250GB/320GB) .

Phones may also be made with a hardware keyboard for text input.  Pressing and holding certain keys will reveal similar characters. The keys are somewhat larger and spaced farther apart when in landscape mode.

Web browser

Windows Phone 7 features a version of Internet Explorer Mobile with a rendering engine that is "halfway between IE7 and IE8  WD  passport essential SE (750GB/1TB ".

Internet Explorer on Windows Phone 7 allows the user to maintain a list of favorite web pages and show a tile linking to a web page on the Start screen. The browser supports up to 6 tabs, which can all load in parallel          WD  passport elite(250GB/320GB) .

Other features include multi-touch gestures, a streamlined UI, smooth zoom in/out animations, the ability to save pictures that are on web pages, share web page

s via email, and support for inline search which allows the user to search for a word or phrase in a web page by typing it     WD passport elite(500GB/640GB) .

Furthermore, Adobe has announced that Flash Player 10.1 will be released for Windows Phone 7. Microsoft has announced plans to regularly update the Windows Phone 7 web browser and its layout engine independently from the Windows Phone Update system  WD  passport studio for Mac(320GB/500GB) .

In a demo, Microsoft said that users will be able to stream YouTube videos from the browser. Clicking on a video from the mobile YouTube website will launch the video in a standalone app and will also add the YouTube video to the Music + Video Hub  WD  passport studio for Mac(500GB/640GB) .

A version of the currently unreleased Internet Explorer 9 is also in development for the Windows Phone OS, which is to include better HTML, CSS and JavaScript standards support, as well as hardware acceleration.


Contacts are organized via the "People hub". Contacts can be manually entered into contacts or import from Facebook  WD  Elements series(250GB/320GB) .

A "What's New" section show news feed fromFacebook and Windows Live updates made by your contacts. A "Me" section show the phone user's own Facebook status and wall. Contacts can be added to the home screen by pinning them to the start   WD  Elements SE(500GB/640GB) .

The contact's "Live Tile" displays their Facebook status and profile picture on the homescreen and the contact's hub displays their Facebook wall as well as all of the rest of their contact information.

Integration of Twitter into the People Hub has been announced to be coming in a software update in the first half of 2011  WD Elements SE(750GB/1TB) .


Setup support Hotmail, Outlook, Yahoo! Mail, Gmail, and other email services and also features support for POP and IMAP accounts. Contacts and calendars are sync along with emails. Users can also search through email with keywords in email contents, subjects, senders, and receivers        WD  Elements desktop(500GB/640GB) .


Zune for Windows Phone 7 is an application providing entertainment and synchronization capabilities between PC and Phone.[46]Windows Phone 7 multimedia experience is divided in to two distinct hubs, Music + Videos hub and Pictures hub, both of which are similar in appearance and functionality to that of the Zune HD         WD  Elements desktop(750GB/1TB) .

The "Music + Videos hub" plays music, videos, and podcasts, and allows users to access the Zune Marketplace to buy music or rent it with the Zune Pass subscription service, and view artist biographies and photos            WD  Elements desktop(1.5 TB/2TB) .

The "Pictures hub" displays the user's Facebook and Windows Live photo albums alongside photos taken with the phone's camera. Users can also upload photos to social networks and comment on online photos directly from the Pictures hub. Multi-touch gestures permit zooming in and out of photos      WD  passport essential SE (750GB/1TB)--USB 3.0).


Xbox Live on Windows Phone 7 brings Console-like gaming experience to phones by displaying the user's avatar in a 3D fashion. Via "Games Hub", the users are able to interact with the avatar, view gamerscore and leaderboards, message Xbox Live friends, and Spotlight        WD  passport essential (500GB/640GB) .

Multiplayer (turn-based) gaming with live multiplayer are also released. Microsoft has unveiled more than 50 premium Windows Phone 7 Games titles at Gamescom that makes use of Xbox Live on mobile. Furthermore, as of now, Xbox Live on Windows Phone 7 is not offering any real-time multiplayer games but the current development is signifying the chances in future   WD  passport for Mac(320GB/500GB).

Some key features of Xbox Live on Windows Phone 7 include ability to be signed in simultaneously on the console and phone, send and receive messages between Console and Phone, unique gamer points only available by purchasing the gaming title on the phone, etc      WD  passport for Mac(640GB/1TB) .


Microsoft's hardware requirements stipulate that every Windows Phone must have a dedicated Search button on the front of the device that performs different actions. Pressing the search button while an application is open will allow users to search within applications that take advantage of this feature         My book essential 4 generation  (640GB/1TB) ;

for example, pressing Search in the People hub will let the users search their contact list for specific people.

In other cases, pressing the Search button will allow the user to perform a search of web sites, news, and map locations using the Bing application       WD  My book essential 4 generation( 1.5TB/2TB).

Windows Phone 7 also has a voice recognition function, powered by TellMe, which allows the user to perform a Bing search, call contacts or launch applications by speaking. This can be activated by pressing and holding the phone's Start button   WD  My book elite( 1TB/1.5TB) .

Bing is the default search engine on Windows Phone 7 handsets due to the deep integration of functions into the OS (which also include the utilization of its map servicefor location-based searches and queries). However, Microsoft has stated that other search engine applications can be used     WD  My book studio(1TB/2TB) .

Office suite

The "Office hub" organized all Microsoft Office programs and documents. Microsoft Office Mobile provide operability between Windows Phone 7 and the desktop version of Microsoft Office. Word Mobile, Excel Mobile, PowerPoint Mobile, OneNote Mobile, and SharePoint Workspace Mobile allow Microsoft Office file format to be viewed and edited  WD  My book essential 4 generation( 1.5TB/2TB).

At Mobile World Congress 2011, Microsoft announced that they would support Office documents in the cloud on Windows Phone 7 after an update in the second half of 2011   WD  My book elite(640GB/2TB) .

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14 février 2011 1 14 /02 /février /2011 14:45

A solar cell (also called photovoltaic cell) is a solid state device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Assemblies of cells are used to make solar modules, also known as solar panels  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

The energy generated from these solar modules, referred to as solar power, is an example of solar energy.

Photovoltaics is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight  Dell Studio XPS 1640 Battery .

Cells are described as photovoltaic cells when the light source is not necessarily sunlight. These are used for detecting light or other electromagnetic radiation near the visible range, for example infrared detectors, or measurement of light intensity  Dell Vostro 1710 Battery .

History of solar cells

The term "photovoltaic" comes from the Greek ??? (ph?s) meaning "light", and "voltaic", meaning electric, from the name of the Italian physicist Volta, after whom a unit of electro-motive force, the volt, is named. The term "photo-voltaic" has been in use in English since 1849     Dell KM958 battery .

The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated thesemiconductor selenium with an extremely thin layer of gold to form the junctions   Dell Studio 1555 battery .

The device was only around 1% efficient. In 1888 Russian physicist Aleksandr Stoletov built the first photoelectric cell(based on the outer photoelectric effect discovered by Heinrich Hertz earlier in 1887). Albert Einstein explained the photoelectric effect in 1905 for which he received the Nobel prize in Physics in 1921   Sony VGP-BPS13 battery .

Russell Ohl patented the modern junction semiconductor solar cell in 1946, which was discovered while working on the series of advances that would lead to the transistor.

Bell produces the first practical cell

The modern photovoltaic cell was developed in 1954 at Bell Laboratories Sony VGP-BPS13/B battery .

The highly efficient solar cell was first developed by Daryl Chapin, Calvin Souther Fuller and Gerald Pearson in 1954 using a diffused silicon p-n junction. At first, cells were developed for toys and other minor uses, as the cost of the electricity they produced was very high - in relative terms, a cell that produced 1 watt of electrical power in bright sunlight cost about $250, comparing to 2 to $3 for a coal plant   Sony VGP-BPS13/S battery .

Solar cells were rescued from obscurity by the suggestion to add them to the Vanguard I satellite. In the original plans, the satellite would be powered only by battery, and last a short time while this ran down. By adding cells to the outside of the fuselage, the mission time could be extended with no major changes to the spacecraft or its power systems   Sony VGP-BPS13A/B battery .

There was some skepticism at first, but in practice the cells proved to be a huge success, and solar cells were quickly designed into many new satellites, notably Bell's own Telstar.

Improvements were slow over the next two decades, and the only widespread use was in space applications where their power-to-weight ratio was higher than any competing technology   Sony VGP-BPS13B/B battery .

However, this success was also the reason for slow progress; space users were willing to pay anything for the best possible cells, there was no reason to invest in lower-cost solutions if this would reduce efficiency. Instead, the price of cells was determined largely by the semiconductor industry     Sony VGP-BPL9 battery ;

their move to integrated circuits in the 1960s led to the availability of larger boules at lower relative prices. As their price fell, the price of the resulting cells did as well. However these effects were limited, and by 1971 cell costs were estimated to be $100 a wattSony VGP-BPS13B/B battery .

Berman's price reductions

In the late 1960s, Elliot Berman was investigating a new method for producing the silicon feedstock in a ribbon process. However, he found little interest in the project and was unable to gain the funding needed to develop it   Sony VGP-BPL15 battery .

In a chance encounter, he was later introduced to a team at Exxon who were looking for projects 30 years in the future. The group had concluded that electrical power would be much more expensive by 2000, and felt that this increase in price would make new alternative energy sources more attractive, and solar was the most interesting among these   Dell Inspiron E1505 battery .

In 1969, Berman joined the Linden, New Jersey Exxon lab, Solar Power Corporation (SPC).

His first major effort was to canvas the potential market to see what possible uses for a new product were, and they quickly found that if the dollars per watt was reduced from then-current $100/watt to about $20/watt there was significant demand  Dell Latitude E6400 battery .

Knowing that his ribbon concept would take years to develop, the team started looking for ways to hit the $20 price point using existing materials.

The first improvement was the realization that the existing cells were based on standard semiconductor manufacturing process, even though that was not ideal      HP Pavilion dv6000 Battery .

This started with the boule, cutting it into disks called wafers, polishing the wafers, and then, for cell use, coating them with an anti-reflective layer. Berman noted that the rough-sawn wafers already had a perfectly suitable anti-reflective front surface, and by printing the electrodes directly on this surface, two major steps in the cell processing were eliminated   SONY VAIO VGN-FZ Battery .

The team also explored ways to improve the mounting of the cells into arrays, eliminating the expensive materials and hand wiring used in space applications with a printed circuit board on the back, acrylic plastic on the front, and silicone based glue between the two potting the cells    SONY VAIO VGN-FZ18 Battery .

But the largest improvement in price point was Berman's realization that existing silicon was effectively "too good" for solar cell use; the minor imperfections that would ruin a boule (or individual wafer) for electronics would have little effect in the solar applicationSONY VAIO VGN-FZ21E Battery .

Putting all of these changes into practice, the company started buying up "reject" silicon from existing manufacturers at very low cost. By using the largest wafers available, thereby reducing the amount of wiring for a given panel area, and packaging them into panels using their new methods      SONY VAIO VGN-FW21E Battery ,

by 1973 SPC was producing panels at $10 and selling them at $20, a fivefold decrease in prices in two years.

Navigation market

SPC approached companies making buoys as a natural market for their products, but found a curious situation  SONY VAIO VGN-NR11S/S Battery .

The primary company in the business was Automatic Power, a battery manufacturer. Realizing that solar cells might eat into their battery profits, Automatic purchased the rights to earlier solar cell designs and suppressed them. Seeing there was no interest there, SPC turned toTideland Signal, another battery company formed by ex-Automatic managers   SONY VAIO VGN-NR11M/S Battery .

Tideland introduced a solar-powered buoy and was soon ruining Automatic's business.

The timing could not be better; the rapid increase in the number of offshore oil platforms and loading facilities produced an enormous market among the oil companies       SONY VAIO VGN-NR11Z/S Battery .

As Tideland's fortunes improved, Automatic started looking for their own supply of solar panels. They found Bill Yerks of Solar Power International (SPI) in California, who was looking for a market. SPI was soon bought out by one of its largest customers, the ARCO oil giant, forming ARCO Solar       SONY VAIO VGN-NR11Z/T Battery .

ARCO Solar's factory in Camarillo, California was the first dedicated to building solar panels, and has been in continual operation from its purchase by ARCO in 1977 to this day.

This market, combined with the 1973 oil crisis, led to a curious situation     Sony VAIO VGN-FZ21E Battery .

Oil companies were now cash-flush due to their huge profits during the crisis, but were also acutely aware that their future success would depend on some other form of power. Over the next few years, the major oil companies started a number of solar firms, and were for decades the largest producers of solar panels      Sony VAIO VGN-FW21E Battery .

Exxon, ARCO, Shell, Amoco (later purchased by BP) and Mobil all had major solar divisions during the 1970s and 80s. Technology companies also had some investment, including General Electric, Motorola, IBM, Tyco and RCA  Sony VAIO VGN-NR11S/S Battery .

Further improvements

In the time since Berman's work, improvements have brought production costs down under $1 a watt, with wholesale costs on the order of $2. "Balance of system" costs are now more than the panels themselves, with large commercial arrays falling to around $5 a watt, fully commissioned, in 2010       Sony VAIO VGN-NR11Z/S Battery .

As the semiconductor industry moved to ever-larger boules, older equipment became available at fire-sale prices. Cells have grown in size as older equipment became available on the surplus market; ARCO Solar's original panels used cells with 2 to 4 inch diameter  Sony VAIO VGN-NR11M/S Battery .

Panels in the 1990s and early 2000s generally used 5 inch wafers, and since 2008 almost all new panels use 6 inch cells. Another major change was the move to polycrystalline silicon. This material has less efficiency, but is less expensive to produce in bulk  Sony VAIO VGN-NR11Z/T Battery .

The widespread introduction of flat screen televisions in the late 1990s and early 2000s led to the wide availability of large sheets of high-quality glass, used on the front of the panels.

Other technologies have also come to market   SONY VAIO VGN-FZ180E Battery .

First Solar has grown to become the largest panel manufacturer, in terms of yearly power produced, using a thin-film cell sandwiched between two layers of glass. This was the first product to beat $1 a watt for production costs.  Since then a glut of polycrystalline silicon has pushed prices of conventional panels into the same range   SONY VAIO VGN-FZ220E Battery .


Solar cells are often electrically connected and encapsulated as a module. Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from abrasion and impact due to wind-driven debris, rain, hail, et cetera   SONY VAIO VGN-FZ340E Battery .

Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and current   SONY VAIO VGN-FZ430E Battery .

To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connected photovoltaic systems); in stand-alone systems, batteries are used to store the energy that is not needed immediately. Solar panels can be used to power or recharge portable devices  SONY VAIO VGN-FZ460E Battery .


The solar cell works in three steps:

  1. Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon  SONY VAIO VGN-FZ480E Battery .
  2. Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction.
  3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity  SONY VAIO VGN-FZ4000 Battery .


The efficiency of a solar cell may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies  SONY VAIO VGN-FZ31E Battery .

Due to the difficulty in measuring these parameters directly, other parameters are measured instead: thermodynamic efficiency, quantum efficiency, VOCratio, and fill factor. Reflectance losses are a portion of the quantum efficiency under "external quantum efficiency"   SONY VAIO VGN-FZ31B Battery .

Recombination losses make up a portion of the quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of the quantum efficiency, VOC ratio.

Crystalline silicon devices are now approaching the theoretical limiting efficiency of 29%  SONY VAIO VGN-FZ31J Battery .


The cost of a solar cell is given per unit of peak electrical power. Manufacturing costs necessarily include the cost of energy required for manufacture. Solar-specific feed in tariffs vary worldwide, and even state by state within various countries   SONY VAIO VGN-FZ31M Battery .

Such feed-in tariffs can be highly effective in encouraging the development of solar power projects.

High-efficiency solar cells are of interest to decrease the cost of solar energy. Many of the costs of a solar power plant are proportional to the area of the plant   SONY VAIO VGN-FZ31Z Battery ;

a higher efficiency cell may reduce area and plant cost, even if the cells themselves are more costly. Efficiencies of bare cells, to be useful in evaluating solar power plant economics, must be evaluated under realistic conditions. The basic parameters that need to be evaluated are the short circuit current, open circuit voltage  SONY VAIO VGN-FZ38M Battery .

The chart at the right illustrates the best laboratory efficiencies obtained for various materials and technologies, generally this is done on very small, i.e. one square cm, cells. Commercial efficiencies are significantly lower   SONY VGP-BPS8 Battery .

A low-cost photovoltaic cell is a thin-film cell intended to produce electrical energy at a price competitive with traditional (fossil fuels and nuclear power) energy sources. This includes second and third generation photovoltaic cells, that is cheaper than first generation (crystalline silicon cells, also called wafer or bulk cells)  SONY VGP-BPS13/S Battery .

Grid parity, the point at which photovoltaic electricity is equal to or cheaper than grid power, can be reached using low cost solar cells. It is achieved first in areas with abundant sun and high costs for electricity such as in California and Japan. Grid parity has been reached in Hawaii and other islands that otherwise use diesel fuel to produce electricity   SONY VGP-BPS13A/B Battery .

George W. Bush had set 2015 as the date for grid parity in the USA.Speaking at a conference in 2007, General Electric's Chief Engineer predicted grid parity without subsidies in sunny parts of the United States by around 2015      SONY VGP-BPS13B/B Battery .

The price of solar panels fell steadily for 40 years, until 2004 when high subsidies in Germany drastically increased demand there and greatly increased the price of purified silicon (which is used in computer chips as well as solar panels)   SONY VGP-BPS13A/S Battery .

One research firm predicted that new manufacturing capacity began coming on-line in 2008 (projected to double by 2009) which was expected to lower prices by 70% in 2015. Other analysts warned that capacity may be slowed by economic issues, but that demand may fall because of lessening subsidies   SONY VGP-BPS13AS Battery .

Other potential bottlenecks which have been suggested are the capacity of ingot shaping and wafer slicing industries, and the supply of specialist chemicals used to coat the cells.


The Shockley-Queisser limit for the theoretical maximum efficiency of a solar cell. Semiconductors with bandgap between 1 and 1.5eV have the greatest potential to form an efficient cell   Dell Inspiron 1320n Battery .

(The efficiency "limit" shown here can be exceeded bymultijunction solar cells.)

Different materials display different efficiencies and have different costs. Materials for efficient solar cells must have characteristics matched to the spectrum of available light       Dell Inspiron 1464 Battery .

Some cells are designed to efficiently convert wavelengths of solar light that reach the Earth surface. However, some solar cells are optimized for light absorption beyond Earth's atmosphere as well. Light absorbing materials can often be used in multiple physical configurations to take advantage of different light absorption and charge separation mechanisms  Dell Inspiron 1564 Battery .

Materials presently used for photovoltaic solar cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide/sulfide  Dell Inspiron 1764 Battery .

Many currently available solar cells are made from bulk materials that are cut into wafers between 180 to 240 micrometers thick that are then processed like other semiconductors      Dell Studio 1450 Battery .

Other materials are made as thin-films layers, organic dyes, and organic polymers that are deposited on supporting substrates. A third group are made fromnanocrystals and used as quantum dots (electron-confined nanoparticles). Silicon remains the only material that is well-researched in both bulk and thin-filmforms     Dell Studio 1457 Battery .

Crystalline silicon

By far, the most prevalent bulk material for solar cells is crystalline silicon (abbreviated as a group as c-Si), also known as "solar grade silicon". Bulk silicon is separated into multiple categories according to crystallinity and crystal size in the resulting ingot, ribbon, or wafer  Dell Latitude D610 Battery .

  1. monocrystalline silicon (c-Si): often made using the Czochralski process. Single-crystal wafer cells tend to be expensive, and because they are cut from cylindrical ingots, do not completely cover a square solar cell module without a substantial waste of refined silicon. Hence most c-Si panels have uncovered gaps at the four corners of the cells  Toshiba NB100 Battery .
  2. Poly- or multicrystalline silicon (poly-Si or mc-Si): made from cast square ingots — large blocks of molten silicon carefully cooled and solidified. Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient. US DOE data shows that there were a higher number of multicrystalline sales than monocrystalline silicon sales  Toshiba Satellite M65 battery .
  3. Ribbon silicon is a type of multicrystalline silicon: it is formed by drawing flat thin films from molten silicon and results in a multicrystalline structure. These cells have lower efficiencies than poly-Si, but save on production costs due to a great reduction in silicon waste, as this approach does not require sawing from ingots   Toshiba Satellite M60 battery .

Analysts have predicted that prices of polycrystalline silicon will drop as companies build additional polysilicon capacity quicker than the industry’s projected demand. On the other hand, the cost of producing upgraded metallurgical-grade silicon, also known as UMG Si, can potentially be one-sixth that of making polysilicon   Dell Latitude D830 Battery .

Manufacturers of wafer-based cells have responded to thin-film lower prices with rapid reductions in silicon consumption. According to Jef Poortmans, director of IMEC's organic and solar department, current cells use between eight and nine grams of silicon per watt of power generation, with wafer thicknesses in the neighborhood of 0.200 mm   Dell Latitude D620 Battery .

At 2008 spring's IEEE Photovoltaic Specialists' Conference (PVS'08), John Wohlgemuth, staff scientist at BP Solar, reported that his company has qualified modules based on 0.180 mm thick wafers and is testing processes for 0.16 mm wafers cut with 0.1 mm wire  Dell Inspiron Mini 10 Battery .

IMEC's roadmap, presented at the organization's recent annual research review meeting, envisions use of 0.08 mm wafers by 2015.

Thin films

Thin-film technologies reduce the amount of material required in creating a solar cell   Sony VGN-FW11S Battery .

Though this reduces material cost, it may also reduce energy conversion efficiency. Thin-film silicon cells have become popular due to cost, flexibility, lighter weight, and ease of integration, compared to wafer silicon cells   Sony VGN-FW11M Battery .

Cadmium telluride solar cell

A cadmium telluride solar cell use a cadmium telluride (CdTe) thin film, a semiconductor layer to absorb and convert sunlight into electricity. Solarbuzz  has reported that the lowest quoted thin-film module price stands at US$1.76 per watt-peak, with the lowest crystalline silicon (c-Si) module at $2.48 per watt-peak   Sony VGN-FW139E/H battery .

The cadmium present in the cells would be toxic if released. However, release is impossible during normal operation of the cells and is unlikely during ?res in residential roofs. A square meter of CdTe contains approximately the same amount of Cd as a single C cell Nickel-cadmium battery, in a more stable and less soluble form   Dell Latitude E5400 Battery .

Copper-Indium Selenide

Copper indium gallium selenide (CIGS) is a direct-bandgap material. It has the highest efficiency (~20%) among thin film materials (see CIGS solar cells). Traditional methods of fabrication involve vacuum processes including co-evaporation and sputtering   Dell Latitude E4200 Battery .

Recent developments at IBM and Nanosolar have been targeting to lower the cost by using non-vacuum solution processes.

Gallium arsenide multijunction

High-efficiency multijunction cells were originally developed for special applications such as satellites and space exploration, but at present, their use in terrestrial concentrators might be the lowest cost alternative in terms of $/kWh and $/W  Dell Inspiron 300M Battery .

These multijunction cells consist of multiple thin films produced using metalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconductors: GaAs, Ge, and GaInP2.Each type of semiconductor will have a characteristic band gap energy which   Dell Vostro A840 Battery ,

loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum. The semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible   Dell Studio 1737 battery .

GaAs based multijunction devices are the most efficient solar cells to date. In October 2010, triple junction metamorphic cell reached a record high of 42.3%.

This technology is currently being utilized in the Mars Exploration Rover missions which have run far past their 90 day design life  Dell Inspiron E1505 battery .

Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge pn junctions, are seeing demand rapidly rise. In just the past 12 months (12/2006 – 12/2007), the cost of 4N gallium metal has risen from about $350 per kg to $680 per kg   Dell RM791 battery .

Additionally, germanium metal prices have risen substantially to $1000–$1200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry  Dell XPS M1530 battery .

Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time World Solar Challenge winners Nuna in 2003, 2005 and 2007, and also by the Dutch solar cars Solutra (2005), Twente One (2007) and 21Revolution (2009)  Dell XPS M2010 battery .

The Dutch Radboud University Nijmegen set the record for thin film solar cell efficiency using a single junction GaAs to 25.8% in August 2008 using only 4 µm thick GaAs layer which can be transferred from a wafer base to glass or plastic film   Acer Aspire One battery .

Light-absorbing dyes (DSSC)

Dye-sensitized solar cells (DSSCs) are made of low-cost materials and do not need elaborate equipment to manufacture, so they can be made in a DIY fashion, possibly allowing players to produce more of this type of solar cell than others   Toshiba Satellite P10 Battery .

In bulk it should be significantly less expensive than older solid-state cell designs. DSSC's can be engineered into flexible sheets, and although its conversion efficiency is less than the best thin film cells, its price/performance ratio should be high enough to allow them to compete with fossil fuel electrical generation   SONY VGN-FZ210CE Battery .

The DSSC has been developed by Prof.Michael Grätzel in 1991 at the Swiss Federal Institute of Technology (EPFL) in Lausanne (CH).

Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of light-absorbing material  Dell Precision M70 Battery.

The dye-sensitized solar cell depends on a mesoporous layer of nanoparticulate titanium dioxide to greatly amplify the surface area (200–300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from the light absorbing dye are passed on to the n-type TiO2, and the holes are absorbed by an electrolyte on the other side of the dye  Toshiba Satellite L305 Battery .

The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows a more flexible use of materials, and is typically manufactured by screen printing and/or use of Ultrasonic Nozzles, with the potential for lower processing costs than those used for bulk solar cells   Toshiba Satellite T4900 Battery .

However, the dyes in these cells also suffer from degradation under heat and UV light, and the cell casing is difficult to seal due to the solvents used in assembly. In spite of the above, this is a popular emerging technology with some commercial impact forecast within this decade     Toshiba PA3399U-2BRS battery .

The first commercial shipment of DSSC solar modules occurred in July 2009 from G24i Innovations (www.g24i.com).

Organic/polymer solar cells

Organic solar cells are a relatively novel technology, yet hold the promise of a substantial price reduction (over thin-film silicon) and a faster return on investment    Toshiba Satellite A200 Battery .

These cells can be processed from solution, hence the possibility of a simple roll-to-roll printing process, leading to inexpensive, large scale production.

Organic solar cells and polymer solar cells are built from thin films (typically 100 nm) of organic semiconductors including polymers    Toshiba Satellite 1200 Battery ,

such as polyphenylene vinylene and small-molecule compounds like copper phthalocyanine (a blue or green organic pigment) and carbon fullerenes and fullerene derivatives such as PCBM. Energy conversion efficiencies achieved to date using conductive polymers are low compared to inorganic materials     Toshiba Satellite M300 Battery .

However, it has improved quickly in the last few years and the highest NREL (National Renewable Energy Laboratory) certified efficiency has reached 6.77%. In addition, these cells could be beneficial for some applications where mechanical flexibility and disposability are important      SONY VGP-BPS13A/Q Battery .

These devices differ from inorganic semiconductor solar cells in that they do not rely on the large built-in electric field of a PN junction to separate the electrons and holes created when photons are absorbed. The active region of an organic device consists of two materials, one which acts as an electron donor and the other as an acceptor   SONY VGP-BPS13A/Q Battery .

When a photon is converted into an electron hole pair, typically in the donor material, the charges tend to remain bound in the form of an exciton, and are separated when the exciton diffuses to the donor-acceptor interface. The short exciton diffusion lengths of most polymer systems tend to limit the efficiency of such devices   SONY VGP-BPS13B/Q Battery .

Nanostructured interfaces, sometimes in the form of bulk heterojunctions, can improve performance.

Silicon thin films

Silicon thin-film cells are mainly deposited by chemical vapor deposition (typically plasma-enhanced (PE-CVD)) from silane gas and hydrogen gas      SONY VGP-BPS13B/Q Battery .

Depending on the deposition parameters, this can yield:

  1. Amorphous silicon (a-Si or a-Si:H)
  2. Protocrystalline silicon or
  3. Nanocrystalline silicon (nc-Si or nc-Si:H), also called microcrystalline silicon   SONY VGP-BPS13/Q Battery .

It has been found that protocrystalline silicon with a low volume fraction of nanocrystalline silicon is optimal for high open circuit voltage.[30] These types of silicon present dangling and twisted bonds, which results in deep defects (energy levels in the bandgap) as well as deformation of the valence and conduction bands (band tails)   SONY VGP-BPS13/Q Battery .

The solar cells made from these materials tend to have lowerenergy conversion efficiency than bulk silicon, but are also less expensive to produce. The quantum efficiency of thin film solar cells is also lower due to reduced number of collected charge carriers per incident photon   SONY VGP-BPS21A/B Battery .

An amorphous silicon (a-Si) solar cell is made of amorphous or microcrystalline silicon and its basic electronic structure is the p-i-n junction. As the amorphous structure has a higher absorption rate of light than crystalline cells, the complete light spectrum can be absorbed with a very thin layer of photo-electrically active material   SONY VGP-BPS21/S Battery .

A film only 1 micron thick can absorb 90% of the usable solar energy.The production of a-Si thin film solar cells uses glass as a substrate and deposits a very thin layer of silicon by plasma-enhanced chemical vapor deposition (PECVD)   SONY VGP-BPS21B Battery .

A-Si manufacturers are working towards lower costs per watt and higher conversion efficiency with continuous research and development on Multijunction solar cells for solar panels. Anwell Technologies Limited recently announced its target for multi-substrate-multi-chamber PECVD, to lower the cost to USD0.5 per watt  SONY VGP-BPS21A Battery .

Amorphous silicon has a higher bandgap (1.7 eV) than crystalline silicon (c-Si) (1.1 eV), which means it absorbs the visible part of the solar spectrum more strongly than the infrared portion of the spectrum. As nc-Si has about the same bandgap as c-Si, the nc-Si and a-Si can advantageously be combined in thin layers, creating a layered cell called a tandem cell SONY VGP-BPS21 Battery .

The top cell in a-Si absorbs the visible light and leaves the infrared part of the spectrum for the bottom cell in nc-Si.

Recently, solutions to overcome the limitations of thin-film crystalline silicon have been developed   Sony VGP-BPS21A/B Battery .

Light trapping schemes where the weakly absorbed long wavelength light is obliquely coupled into the silicon and traverses the film several times can significantly enhance the absorption of sunlight in the thin silicon films. Thermal processing techniques can significantly enhance the crystal quality of the silicon and thereby lead to higher efficiencies of the final solar cells  Sony VGP-BPS21/S Battery .


Because solar cells are semiconductor devices, they share many of the same processing and manufacturing techniques as other semiconductor devices such as computer and memory chips   Sony VGP-BPS21A Battery .

However, the stringent requirements for cleanliness and quality control of semiconductor fabrication are a little more relaxed for solar cells. Most large-scale commercial solar cell factories today make screen printed poly-crystalline silicon solar cells   Sony VGP-BPS21 Battery .

Single crystalline wafers which are used in the semiconductor industry can be made into excellent high efficiency solar cells, but they are generally considered to be too expensive for large-scale mass production    Sony Vaio PCG-5G2L Battery .

Poly-crystalline silicon wafers are made by wire-sawing block-cast silicon ingots into very thin (180 to 350 micrometer) slices or wafers. The wafers are usually lightly p-type doped. To make a solar cell from the wafer, a surface diffusion of n-type dopants is performed on the front side of the wafer     Sony Vaio PCG-5G3L Battery .

This forms a p-n junction a few hundred nanometers below the surface.

Antireflection coatings, to increase the amount of light coupled into the solar cell, are typically next applied   Sony Vaio PCG-5J1L Battery .

Silicon nitride has gradually replaced titanium dioxide as the antireflection coating because of its excellent surface passivation qualities. It prevents carrier recombination at the surface of the solar cell. It is typically applied in a layer several hundred nanometers thick using plasma-enhanced chemical vapor deposition (PECVD)   Sony Vaio PCG-5K2L Battery .

Some solar cells have textured front surfaces that, like antireflection coatings, serve to increase the amount of light coupled into the cell. Such surfaces can usually only be formed on single-crystal silicon, though in recent years methods of forming them on multicrystalline silicon have been developed       Sony Vaio PCG-5J2L Battery .

The wafer then has a full area metal contact made on the back surface, and a grid-like metal contact made up of fine "fingers" and larger "busbars" are screen-printed onto the front surface using a silverpaste. The rear contact is also formed by screen-printing a metal paste, typically aluminium       Sony Vaio PCG-5K1L Battery .

Usually this contact covers the entire rear side of the cell, though in some cell designs it is printed in a grid pattern. The paste is then fired at several hundred degrees celsius to form metal electrodes in ohmic contact with the silicon. Some companies use an additional electro-plating step to increase the cell efficiency      Sony Vaio PCG-5L1L Battery .

After the metal contacts are made, the solar cells are interconnected in series (and/or parallel) by flat wires or metal ribbons, and assembled into modules or "solar panels". Solar panels have a sheet of tempered glass on the front, and a polymer encapsulation on the back       Sony Vaio PCG-6S2L Battery .


Most commercially available solar cells are capable of producing electricity for at least twenty years without a significant decrease in efficiency. The typical warranty given by panel manufacturers is for a period of 25 – 30 years, wherein the output shall not fall below a specified percentage (around 80%) of the rated capacity       Sony Vaio PCG-6S3L Battery .

Research topics

There are currently many research groups active in the field of photovoltaics in universities and research institutions around the world        Sony Vaio PCG-6V1L Battery .

This research can be divided into three areas: making current technology solar cells cheaper and/or more efficient to effectively compete with other energy sources; developing new technologies based on new solar cell architectural designs; and developing new materials to serve as light absorbers and charge carriers       Sony Vaio PCG-6W1L Battery .

Manufacturers and certification

National Renewable Energy Laboratory tests and validates solar technologies. There are three reliable certifications of solar equipment: UL and IEEE (both U.S. standards) and IEC       Sony Vaio PCG-6W2L Battery .

Solar cells are manufactured primarily in Japan, Germany, Mainland China, Taiwan and United States, though numerous other nations have or are acquiring significant solar cell production capacity. While technologies are constantly evolving toward higher efficiencies      Sony Vaio PCG-6W3L Battery ,

the most effective cells for low cost electrical production are not necessarily those with the highest efficiency, but those with a balance between low-cost production and efficiency high enough to minimize area-related balance of systems cost     Sony Vaio PCG-7111L Battery .

Those companies with large scale manufacturing technology for coating inexpensive substrates may, in fact, ultimately be the lowest cost net electricity producers, even with cell efficiencies that are lower than those of single-crystal technologies  Sony Vaio PCG-7112L Battery .


Backed by Chinese government's unprecedented plan to offer subsidies for utility-scale solar power projects that is likely to spark a new round of investment from Chinese solar panel makers. Chinese companies have already played a more important role in solar panels manufacturing in recent years      Sony Vaio PCG-7113L Battery .

China produced solar cells/modules with an output of 1,180 MW in 2007 making it the largest producer in the world, according to statistics from China Photovoltaic Association.Some Chinese companies such as Suntech Power    Sony Vaio PCG-7133L Battery ,

Yingli, LDK Solar Co, JA Solar and ReneSola have already announced projects in cooperation with regional governments with hundreds of megawatts each after the ‘Golden Sun’ incentive program was announced by the government   Sony Vaio PCG-7Z2L Battery .

The new development of solar module manufacturers with thin-film technology such as Veeco and Anwell Technologies Limited will further help to boost the domestic solar industry        Sony Vaio PCG-8Y1L Battery .

United States

New manufacturing facilities for solar cells and modules in Massachusetts, Michigan, New York, Ohio, Oregon, and Texas promise to add enough capacity to produce thousands of megawatts of solar devices per year within the next few years from 2008   Sony Vaio PCG-8Y2L Battery .

In late September 2008, Sanyo Electric Company, Ltd. announced its decision to build a manufacturing plant for solar ingots and wafers in Salem, Oregon. The plant will begin operating in October 2009 and will reach its full production capacity of 70 megawatts (MW) of solar wafers per year by April 2010      Sony Vaio PCG-8Z1L Battery .

In early October 2008, First Solar, Inc. broke ground on an expansion of its Perrysburg, Ohio, facility that will add enough capacity to produce another 57 MW per year of solar modules at the facility, bringing its total capacity to roughly 192 MW per year. The company expects to complete construction early next year and reach full production by mid-2010  Sony Vaio PCG-8Z2L Battery .

In mid-October 2008, SolarWorld AG opened a manufacturing plant in Hillsboro, Oregon, that is expected to produce 500 MW of solar cells per year when it reaches full production in 2011.

Solyndra has a manufacturing facility for its unique tubular CIGS technology in California       Sony VAIO PCG-5G2L Battery .

In March 2010, SpectraWatt, Inc. began production at its manufacturing plant in Hopewell Junction, NY, which was expected to produce 120 MW of solar cells per year when it reaches full production in 2011. However, the closure of this plant was announced in late 2010      Sony VAIO PCG-5G3L Battery .

Multi-junction solar cells are solar cells containing several p-n junctions. This allows to cover a wider part of the light spectrum, but increases the complexicity of the cell design and manufacture.

Much effort has been spent to improve the production of renewable energy       Sony VAIO PCG-5J1L Battery .

One of the most promising technologies is photovoltaic solar panels which convert solar energy into electrical energy. The first solar cell was a c-Si solar cell realised in 1954 by researchers at Bell Labs had an efficiency of 6%. Within fifty years, considerable progress has been made in the field of photovoltaic technology and many different technologies have emerged   Sony VAIO PCG-5K2L Battery.

Nowadays, common c-Si solar cells have a maximum efficiency of 24.7% but new devices like multi-junction (MJ) solar cells are more promising. With the best efficiency of 42.3% as of October 2010 (under a concentration of 406 suns)  they are well-suited for space applications       Sony VAIO PCG-5J2L Battery .

They also have a significant development potential because theoretical efficiency for an infinite number of pn junctions is 86.8%. However, the structure of MJ solar cells is more complex as compared to other photovoltaic devices.

ndustry sells photovoltaic panels that are composed of several modules       Sony VAIO PCG-5K1L Battery .

All modules are connected in series or in parallel and include numerous solar cells. These are composed of a pn junction made of doped silicon and some metallic contacts to guarantee an electrical connection. When photons hit the top surface of the solar cell, they are either reflected or transmitted       Sony VAIO PCG-5L1L Battery .

Those who are transmitted, give their energy h? to an electron. If h? ? Eg, there is direct electron/hole generation. As shown in Figure A, electrons move from the valence band to the conduction band and that holes appear in the valence band   Sony VAIO PCG-6S2L Battery .

In the depletion region, the drift electric field Edrift accelerates both electrons and holes towards their respective n-doped and p-doped regions. The resulting current Ig is called the generation photocurrent. In the quasi-neutral region, the scattering electric field Escatt accelerates holes (electrons) towards p-doped (n-doped) region  Sony VAIO PCG-6S3L Battery ,

which gives a scattering photocurrent Ipscatt (Inscatt). Consequently, due to the accumulation of charges, a potential V and a photocurrent Iph appear. The expression for this photocurrent is obtained by adding generation and scattering photocurrents: Iph = Ig + Inscatt + Ipscatt Sony VAIO PCG-6V1L Battery .

The J-V characteristics (J is current density, i.e. current per area of pn junction) of a solar cell under illumination are simply obtained by shifting the J-V characteristics of a diode in the dark downward by Iph, as shown in Figure B   Sony VAIO PCG-6W1L Battery .

Since solar cells are designed to supply power and not absorb it, the power P = V·Iph must be negative. Hence, the operating point (Vm, Jm) is located in the region where V>0 andIph<0 are chosen so that they maximize the absolute value of the power |P|  Sony VAIO PCG-6W2L Battery .

The fundamental difference between multi-junction solar cells and c-Si solar cells is that there are several pn junctions connected in series instead of one, as illustrated on figure C(a). In order to better cover the solar spectrum AM1.5 (terrestrial reference spectrum for photovoltaic performance evaluation), suitable materials must be chosen for each pn junction  Sony VAIO PCG-6W3L Battery .

First, their band gaps Eg have to be significantly different so that photons of different wavelength ? =hc/(eEg) ? 1.24×10?6/Eg are absorbed. The figure C(b) illustrates this fact by plotting spectral irradiance G(?), which is the source power density at a given wavelength ?       Sony VAIO PCG-7111L Battery .

Secondly, Eg must decrease from top cell to bottom cell so that photons would not all be absorbed by the top cell. Thirdly, the layers have to be electrically optimal for high performances and be stacked on each other         Sony VAIO PCG-7112L Battery .

This necessitates finding materials with better absorption coefficients ?(?), higher minority carrier lifetimes ?minority, higher mobilities µ and similar lattice constants a. The values in Table below justifie the choice of the usual materials used for multi-junction solar cells  Sony VAIO PCG-7113L Battery :

the top cell is generally made in InGaP (Eg = 1.86 eV), the middle cell in InGaAs (Eg = 1.4 eV) and the bottom cell in Ge (Eg = 0.65 eV). The use of germanium is mainly due to its robustness, its low cost and its facility in production      Sony VAIO PCG-7Z1L Battery .

In addition to the benefits listed above, the use of GaAs instead of Si allows to reach higher efficiencies because the efficiency of GaAs cells is 25.1% while the efficiency of c-Si cells is 24.7%      Sony VAIO PCG-7Z2L Battery .

Because the different layers are closely lattice-matched, the fabrication of the device is usually obtained by using the metal-organic chemical vapor deposition (MOCVD). This technique is preferable to the molecular beam epitaxy (MBE) because it ensures high crystal quality and large scale production       Sony VAIO PCG-8Y1L Battery .

Metallic contacts

The metallic contacts in aluminium are low-resistivity electrodes that make contact with the semiconductor layer in GaAs. They are disposed on the two sides of the structure but mainly on the backwards face so that the shadowing on the lightning surface is reduced   WD passport essential (500GB/640GB) .

Anti-reflective coating

Anti-reflective (AR) coating is generally composed of several layers in the case of MJ solar cells. The top AR layer has usually a NaOH surface texturation with several pyramids in order to increase the transmission coefficient T WD passport essential (250GB/320GB) ,

the trapping of the light in the material (because photons cannot easily get out the MJ structure due to pyramids) and therefore, the path length of photons in the material  . On the one hand, the thickness of each AR layer is chosen to get destructive i

nterferences. Therefore, the reflection coefficient R decreases to 1%       WD  passport essential SE (750GB/1TB .

In the case of two AR layers L1 (the top layer, usually SiO2) and L2 (usually TiO2), there must be  to have the same amplitudes for reflected fields and nL1dL1 = 4?min, nL2dL2 = ?min/4 to have opposite phase for reflected fields. On the other hand, the thickness of each AR layer is also chosen to minimize the reflectance at wavelengths for which the photocurrent is the lowest  WD  passport elite(250GB/320GB) .

Consequently, this maximizes JSC by matching currents of the three subcells. As example, because the current generated by the bottom cell is greater than the currents generated by the other cells, the thickness of AR layers is adjusted so that the infrared (IR) transmission (which corresponds to the bottom cell)       WD passport elite(500GB/640GB)

is degraded while the UV transmission (which corresponds to the top cell) is upgraded. Particularly, an AR coating is very important at low wavelengths because, without it, T would be strongly reduced to 70%        WD  passport studio for Mac(320GB/500GB) .

Tunnel junctions

The main goal of tunnel junctions is to provide a low electrical resistance and optically low-loss connection between two subcells.  Without it, the p-doped region of the top cell would be directly connected with the n-doped region of the middle cell  WD  passport studio for Mac(500GB/640GB) .

Hence, a pn junction with opposite direction to the others would appear between the top cell and the middle cell. Consequently, the photovoltage would be lower than if there would be no parasitic diode. In order to decrease this effect, a tunnel junction is used. It is simply a wide band gap, highly doped diode     WD  Elements series(250GB/320GB) .

The high doping reduces the length of the depletion region because

Hence, electrons can easily tunnel through the depletion region. The J-V characteristic of the tunnel junction is very important because it explains why tunnel junctions can be used to have a low electrical resistance connection between two pn junctions  WD  Elements SE(500GB/640GB) .

Figure D shows three different regions: the tunneling region, the negative differential resistance region and the thermal diffusion region. The region where electrons can tunnel through the barrier is called the tunneling region   WD Elements SE(750GB/1TB) .

There, the voltage must be low enough so that energy of some electrons who are tunneling is equal to energy states available on the other side of the barrier. Consequently, current density through the tunnel junction is high (with maximum value of JP, the peak current density) and the slope near the origin is therefore steep  WD  Elements desktop(500GB/640GB) .

Then, the resistance is extremely low and consequently, the voltage too. This is why tunnel junctions are ideal for connecting two pn junctions without having a voltage drop. When voltage is higher, electrons cannot cross the barrier because energy states are no longer available for electrons      WD  Elements desktop(750GB/1TB) .

Therefore, the current density decreases and the differential resistance is negative. The last region, called thermal diffusion region, corresponds to the J-V characteristic of the usual diode               WD  Elements desktop(1.5 TB/2TB) :

In order to avoid the reduction of the MJ solar cell performances, tunnel junctions must be transparent to wavelengths absorbed by the next photovoltaic cell, the middle cell, i.e. EgTunnel > EgMiddleCell          WD  passport essential SE (750GB/1TB)--USB 3.0) .

Window layer and back-surface field

Figure E: (a) Layers and band structure of a window layer. The surface recombination is reduced. (b) Layers and band structure of a BSF layer. The scattering of carriers is reduced        WD  passport essential (500GB/640GB) .

A window layer is used in order to reduce the surface recombination velocity S. Similarly, a back-surface field (BSF) layer reduces the scattering of carriers towards the tunnel junction. The structure of these two layers is the same: it is a heterojunction which catches electrons (holes)      WD  passport for Mac(320GB/500GB) .

Indeed, despite the electric field Ed, these one cannot jump above the barrier formed by the heterojunction because they don't have enough energy, as illustrated in figure E. Hence, electrons (holes) cannot recombine with holes (electrons) and cannot diffuse through the barrier        WD  passport for Mac(640GB/1TB) .

By the way, window and BSF layers must be transparent to wavelengths absorbed by the next pn junction i.e. EgWindow > EgEmitterand EgBSF > EgEmitter. Furthermore, the lattice constant must be close to the one of InGaP and the layer must be highly doped (n ? 1018 cm?3)     My book essential 4 generation  (640GB/1TB) .

J-V characteristic

For maximum efficiency, each subcell should be operated at its optimal J-V parameters, which are not necessarily equal for each subcell. If they are different, the total current through the solar cell is the lowest of the three      WD  My book essential 4 generation( 1.5TB/2TB) .

By approximation,  it results in the same relationship for the short-circuit current of the MJ solar cell: JSC = min (JSC1, JSC2, JSC3)where JSCi(?) is the short-circuit current density at a given wavelength ? for the subcell i WD  My book elite( 1TB/1.5TB) .

Because of the impossibility to obtain JSC1, JSC2, JSC3 directly from the total J-V characteristic, the quantum efficiency QE(?) is utilized. It measures the ratio between the amount of electron-hole pairs created and the incident photons at a given wavelength ?. Let ?i(?) be the photon flux of corresponding incident light in subcell i and QEi(?) be the quantum efficiency of the subcell i WD  My book studio(1TB/2TB) .

By definition, this equates to:

The value of QEi(?) is obtained by linking it with the absorption coefficient ?(?), i.e. the number of photons absorbed per unit of length by a material        WD  My book essential 4 generation( 1.5TB/2TB) .

If it is assumed that each photon absorbed by a subcell creates an electron/hole pair (which is a good approximation), this leads to :

The performances of MJ solar cells can be improved as follows    WD  My book elite(640GB/2TB) .

Firstly, GaAsSb-based heterojunction tunnel diodes, instead of conventional InGaP highly doped tunnel diodes described above, have a lower tunneling distance. Indeed, in the heterostructure formed by GaAsSb and InGaAs, the valence band of GaAsSb is higher than the valence band of the adjoining p-doped layer  Seagate  expansion portable (320GB/500GB) .

Consequently, the tunneling distance dtunnel is reduced and so the tunneling current, which exponentially depends of dtunnel, is increased. Hence, the voltage is lower than that of the InGaP tunnel junction. There are other advantages to use GaAsSb heterojunction tunnel diode         Seagate  expansion (1.5TB/2TB) .

Firstly, the same current can be achieved by using a lower doping.  Secondly, because the lattice constant is larger for GaAsSb than Ge, one can use a wider range of materials for the bottom cell because more materials are lattice-matched to GaAsSb than to Ge  Seagate  Freeagent Desktop (500GB/1TB) .

Secondly, chemical components can be added to some layers. On the one hand, adding about one percent of Indium in each layer better matches lattice constants of the different layers  . Without it, there is about 0.08 percent of mismatching between layers, which contributes to deteriorate the performances of MJ solar cells     Seagate  Freeagent Go(250GB/320GB) .

On the other hand, adding aluminium to the top cell increases its band gap to 1.96 eV. It allows to cover a larger part of the solar spectrum and obtain a higher open-circuit voltage VOC.

Thirdly, the number of pn junctions in the cell can be increased        Seagate  Freeagent Go(500GB/640GB) .

Indeed, the theoretical efficiency of MJ solar cells is 86.8% for an infinite number of pn junctions. However, increasing the number of layers is very difficult in practice. The maximum theoretical efficiency is 37, 50, 56, 72% for 1, 2, 3, 36 pn junctions, respectivelySeagate  Freeagent Go(750GB/1TB) .

Thus with the increasing number of pn junctions, the effiency gain is small but the complexity of production and matching the individual junctions increases dramatically. Instead of increasing the number of subcells, one can optimize their thickness. Particularly, decreasing the thickness of the top cell will increase the transmission coefficient T Seagate  Freeagent Goflex(250GB/320GB) .

Finally, an InGaP hetero-layer between the p-Ge layer and the InGaAs layer can be added in order to create automatically the n-Ge layer by scattering during MOCVD growth and increase significantly the quantum efficiency QE(?) of the bottom cell. InGaP is advantageous because of its high scattering coefficient and low solubility in Ge      Seagate Freeagent Goflex(500GB/640GB) .

Spectral variations

Solar spectrum at the Earth surface changes constantly depending on the weather and sun position. This results in the variation of ?(?), QE(?), ?(?) and thus the short-circuit currents JSCi Seagate  Freeagent Goflex(750GB/1TB) .

As a result, the current densities Ji are not necessarily matched and the total current becomes lower. Spectral variations of the light can be quantified using the average photon energy (APE) which is the ratio between the spectral irradiance G(?) (the power density of the light source in a specific wavelength ?) and the total photon flux density        Seagate  Freeagent Goflex Pro(500GB/750GB) .

It can be shown that a high (low) value for APE means low (high) wavelengths spectral conditions and higher (lower) efficiencies. Thus APE is a good indicator for quantifying the effects of the solar spectrum variations on MJ solar cell performances and has the added advantage of being independent of the device structure and the absorption profile of the device  Seagate  Freeagent Goflex desktop(1TB/2TB) .

Use of light concentrators

Light concentrators allow to increase efficiencies and reduce the cost efficiency ratio. There are two types of light concentrators: refractive lenses like Fresnel lenses and reflective dishes        Seagate  Freeagent go for Mac(320GB/640GB) .

Thanks to these devices, light arriving on a large surface can be concentrated on a small surface, the MJ solar cell. The intensity concentration ratio (or “suns”) is the average intensity of the focused light divided by 0.1 W/m². If its value is X then the MJ current becomes X higher under concentrated illumination       Samsung  G2 protable (250gb/320GB) .

Comparison with other technologies

There are four main categories of photovoltaic cells: c-Si solar cells, thin film solar cells, MJ solar cells and new technologies (including organic solar cells)        Samsung  G2 protable (500GB/640GB) .

Big differences between multi-junction solar cells and other photovoltaic devices can be observed (see the table above). Physically, the main property of a MJ solar cell is to have more than one pn junction in order to catch a larger photon energy spectrum while the main property of the thin film solar cell is to use thin films instead of thick layers in order to decrease the cost efficiency ratioSamsung  S2 protable (320GB/500GB) .

Economically, there are also some differences: MJ solar panels are more expensive than the others. These differences involve different applications for each ones: MJ solar cells are rather used in space while c-Si solar cells are rather used for terrestrian applications      Samsung S1 Mini (120GB/160GB) .

There are also differences in the evolution of efficiency for different types of solar technology. The efficiencies of solar cells and Si solar technology are relatively stable, while the efficiency of solar modules and multi-junction technology are progressing  Samsung  S1 Mini (250GB/320GB) .

It is important to keep in mind that measurements on MJ solar cells are usually made in laboratory, using light concentrators (this is often not the case for the other cells) and under standard test conditions (STCs). STCs prescribe, for the terrestrian application, the AM1.5 spectrum as reference          Samsung story station (1TB/1.5TB) .

This air mass (AM) corresponds to a fix position of the sun in the sky of 48° and a fix power of 833 W/m². Therefore, spectral variations of incident light and environmental parameters are not taken into account under STC. Consequently, performance of MJ solar cells in terrestrial environment is inferior to that achieved in laboratory      Samsung Story station (1.5TB/2TB) .

Moreover, MJ solar cells are created such that currents are matched under STC but not necessarily under field conditions. One can use QE(?) to compare performances of different technologies, butQE(?) contains no information on the matching of currents of subcells        Samsung story station Esata(1TB/1.5TB) .

An important comparison point is rather the output power per unit area generated with the same incident light.


The cost of MJ solar cells is currently too high to allow a high scale use of it for individuals        Samsung  G3 station (1TB/1.5TB) .

The high cost is mainly due to the complex structure and the high price of materials. Nevertheless, with light concentrators under illumination of at least 400 suns, the use of MJ solar panels become possible and profitable.

The environment in space is quite different from the terrestrian one        Maxtor  one touch 4 plus (500GB/750GB) .

Because there is no more atmosphere in space, the solar spectrum is different (AM0) and there is some damage due to radiation particles who are no longer filtered. They are two kinds of damage: ionisation and atomics displacement       Maxtor one touch 4 plus (1TB/1.5TB) .

They should be considered when sending solar panels to space. The comparison with other technologies shows that it is more convenient to use multi-junction solar cells in space. Indeed, it has a higher radiation resistance, a higher efficiency and a lower temperature coefficient   Maxtor cool black(640GB/1TB) .

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