Overblog Suivre ce blog
Editer l'article Administration Créer mon blog
10 avril 2011 7 10 /04 /avril /2011 14:42

The International Telecommunication Union (Union internationale des télécommunications, in French) is the specialized agency of the United Nationswhich is responsible for information and communication technologies  Ibm ThinkPad G40 Battery .

ITU coordinates the shared global use of the radio spectrum, promotes international cooperation in assigning satellite orbits, works to improve telecommunication infrastructure in the developing world and establishes worldwide standards   Ibm ThinkPad X200T Battery .

ITU also organizes worldwide and regional exhibitions and forums, such as ITU TELECOM WORLD, bringing together representatives of government and the telecommunications and ICT industry to exchange ideas, knowledge and technology.

The ITU is active in areas including broadband Internet, latest-generation wireless technologies  Apple A1280 battery ,

aeronautical and maritime navigation, radio astronomy, satellite-based meteorology, convergence in fixed-mobile phone, Internet access, data, voice, TV broadcasting, and next-generation networks.

ITU is based in Geneva, Switzerland, and its membership includes 192 Member States and around 700 Sector Members and Associates  Apple A1281 battery .

ITU sectors

The ITU comprises three sectors, each managing a different aspect of the matters handled by the Union, as well as ITU Telecom:

Radiocommunication (ITU-R) Samsung R522 battery .
Managing the international radio-frequency spectrum and satellite orbit resources is at the heart of the work of the ITU Radiocommunication Sector (ITU-R).
Standardization (ITU-T)
ITU's standards-making efforts are its best-known — and oldest — activity  Samsung P467 battery . ;
known prior to 1992 as the International Telephone and Telegraph Consultative Committee or CCITT (from its French name "Comité consultatif international téléphonique et télégraphique")
Development (ITU-D)  Hp Pavilion dm3 Battery
Established to help spread equitable, sustainable and affordable access to information and communication technologies (ICT).
ITU Telecom organizes major events for the world's ICT community. ITU Telecom World 2011 is ITU Telecom's 40th Anniversary with the first event in 1971  Hp Pavilion dm4 Battery .

A permanent General Secretariat, headed by the Secretary General, manages the day-to-day work of the Union and its sectors.

The ITU's mission

The ITU's mission is to enable the growth and sustained development of telecommunications and information networks Hp Pavilion cq62 Battery ,

and to facilitate universal access to the emerging information society and global economy. The ITU assists in mobilizing the technical, financial, and human resources required by such development  Hp Pavilion cq42 Battery .

A major priority of the ITU is bridging the so-called "digital divide" by building adequate and safe information and communication infrastructure and developing confidence in the use of cyberspace through enhanced online security.

The ITU also concentrates on strengthening emergency communications for disaster prevention and mitigation, especially in less developed regions Hp Pavilion cq72 Battery .

Legal framework of ITU

The basic texts of the ITU are adopted by the Plenipotentiary Conference. In addition to the Constitution and Convention, the consolidated basic texts include the Optional Protocol on the settlement of disputes  Hp cq20 Battery ,

the Decisions, Resolutions and Recommendations in force, as well as the General Rules of Conferences, Assemblies and Meetings of the Union.


The ITU is headed by a Secretary-General, who is elected to a four-year term by the member states at the plenipotentiary conferenceHp 2230 Battery .

At the 17th Plenipotentiary Conference (2006) in Antalya, Turkey, the ITU's member states elected Dr Hamadoun Touré of Mali as Secretary-General of the Union. He was re-elected for a second four-year term at the 18th Plenipotentiary Conference (2010) in Guadalajara, Mexico  Dell Inspiron Mini 12 battery .


Members states of the ITU are 191 of the UN members and the Vatican City.

Observers are: Palestine

Non-members are: Cook Islands, Niue, Palau and the states with limited recognition  Dell XPS M1730 battery .

Membership of ITU is open to governments, which may join the Union as Member States, as well as to private organizations like carriers, equipment manufacturers, funding bodies, research and development organizations and international and regional telecommunication organizations, which can join ITU as Sector Members  Dell XPS M2010 battery .

Private companies and other organizations may elect to join one or more of the Union’s three Sectors, according to their particular sphere of interest. ITU Sector Members also develop the technical standards which will underpin future telecommunication systems and shape tomorrow’s networks and services  Dell Studio XPS 1340 battery .

Finally, Sector Members gain privileged access to restricted first-hand information which can prove highly valuable in their business planning.

World Summit on the Information Society

The ITU was the lead organizing agency of the World Summit on the Information Society (WSIS), a United Nations summit aiming at bridging the digital divide and turning it into digital opportunity for all  Dell Inspiron 9100 battery .

WSIS provided a global forum on the theme of ICTs (Information and Communication Technologies) for development. WSIS was a pledge for building a people-centered development-oriented Information Society. Other big themes of the Summit were Internet governance and Financial mechanisms for meeting the challenges of ICTs for development  Dell Inspiron N4010 battery .

The idea of holding WSIS came from the Tunisian President Ben Ali on the ITU Plenipotentiary Conference in Minneapolis in 1998. The process was launched late in 2002 on the initiative of Kofi Annan. The first phase of the WSIS summit took place in December 2003 in Geneva and the second and final phase took place in Tunis in November 2005  Dell Inspiron N3610 battery .

WSIS Stocktaking Process was initiated în 2004.The WSIS Stocktaking Process is a follow-up to WSIS. Its purpose is to provide a register of activities carried out by governments, international organizations, the business sector, civil society and other entities, in order to highlight the progress made since that landmark event   Dell Inspiron N5010 battery .

Following § 120 of TAIS, ITU has been maintaining the WSIS Stocktaking database as a publicly accessible system providing information on ICT-related initiatives and projects with reference to the 11 WSIS Action Lines   Dell Inspiron N7010 battery .

The Inter-American Telecommunication Commission or Comisión Interamericana de Telecomunicaciones (CITEL) is an entity of the Organization of American States. It was originally created as the Inter-American Electrical Communication Commission at the Fifth International American Conference in May 1923  Dell Inspiron 1464 battery .

CITEL's job is to coordinate telecommunications related mandates of the OAS General Assembly and those enacted during the Summits of the Americas.

The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communication  Dell Inspiron 1564 battery .

Its role is to manage the international radio-frequency spectrum and satellite orbit resources and to develop standards for radiocommunications systems with the objective of ensuring the effective use of the spectrum  Dell Inspiron 1764 battery .

ITU is required, according to its Constitution, to allocate spectrum and register frequency allocation, orbital positions and other parameters of satellites, “in order to avoid harmful interference between radio stations of different countries”  Dell Inspiron 1320 battery .

The international spectrum management system is therefore based on regulatory procedures for frequency coordination, notification and registration.

ITU-R has a permanent secretariat, the Radiocommunication Bureau, based at the ITU HQ in Geneva, Switzerland  Dell Inspiron 1320n battery .

The elected Director of the Bureau is Mr. Valery Timofeev of Russia. First elected by the ITU Membership to the Directorship in 2002, Mr. Timofeev was re-elected for a 2nd 4-year term in November 2006  Dell Vostro 1710 battery .


The CCIR—Comité consultatif international pour la radio, "Consultative Committee on International Radio" or "International Radio Consultative Committee"—was founded in 1927  Dell Vostro 1720 battery .

In 1932 the CCIR and several other organizations (including the original ITU, which had been founded as the International Telegraph Union in 1865) merged to form what would in 1934 become known as the International Telecommunication Union. In 1992, the CCIR became the ITU-R  Dell Studio XPS 1640 battery .

The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU); it coordinates standards for telecommunications. It is based in Geneva, Switzerland   Dell Vostro A840 battery .

The standardization work of ITU dates back to 1865, with the birth of the International Telegraph Union. It became a United Nations specialized agency in 1947, and the International Telegraph and Telephone Consultative Committee (CCITT), (from the French name "Comité Consultatif International Téléphonique et Télégraphique") was created in 1956 Dell Vostro A860 battery .

It was renamed ITU-T in 1993.

ITU has been an intergovernmental public-private partnership organization since its inception and now has a membership of 191 countries (Member States) and over 700 public and private sector companies as well as international and regional telecommunication entities  Dell Studio 1535 battery ,

known as Sector Members and Associates, which undertake most of the work of the Sector.

ITU-T has a permanent secretariat, the Telecommunication Standardization Bureau (TSB), based at the ITU HQ in Geneva, Switzerland. The elected Director of the Bureau is Mr. Malcolm Johnson of the UK  Dell Studio 1735 battery .

Mr. Johnson was elected by the ITU Membership to the Directorship for a 4-year term in November 2006 and was reelected for a second term starting January 2011.

Primary function

The ITU-T mission is to ensure the efficient and timely production of standards covering all fields of telecommunications on a worldwide basis  Dell Vostro 1310 battery ,

as well as defining tariff and accounting principles for international telecommunication services.

The international standards that are produced by the ITU-T are referred to as "Recommendations" (with the word ordinarily capitalized to distinguish its meaning from the ordinary sense of the word "recommendation") Dell Latitude E6400 battery

as they become mandatory only when adopted as part of a national law.

Since the ITU-T is part of the ITU, which is a United Nations specialized agency, its standards carry more formal international weight than those of most other standards development organizations that publish technical specifications of a similar form  Dell Latitude E6400 Battery .


Although the ITU itself dates back to 1865,  the formal standardization processes are more recent.

Two consultative committees were created by the ITU’s 1925 Paris conference to deal with the complexities of the international telephone services (known as CCIF, as the French acronym) and long-distance telegraphy (CCIT) Dell Latitude E6400 Battery .

In view of the basic similarity of many of the technical problems faced by the CCIF and CCIT, a decision was taken in 1956 to merge them to become the single International Telegraph and Telephone Consultative Committee (CCITT, in the French acronym) Dell Latitude E6500 battery .

In 1992, the Plenipotentiary Conference (the top policy-making conference of ITU) saw a reform of ITU, giving the Union greater flexibility to adapt to an increasingly complex, interactive and competitive environment  Dell Latitude E6500 battery .

It was at this time that CCITT was renamed the Telecommunication Standardization Sector (ITU-T), as one of three Sectors of the Union alongside the Radiocommunication Sector (ITU-R) and the Telecommunication Development Sector (ITU-D) Dell Latitude E6500 battery .

Historically, the Recommendations of the CCITT were presented to four-yearly plenary assemblies for endorsement, and the full set of Recommendations were published after each plenary assembly. However, the delays in producing texts, and translating them into other working languages, did not suit the fast pace of change in the telecommunications industry  Dell Latitude E6500 battery .

"Real time" standardization

The rise of the personal computer industry in the early 1980s created a new common practice among both consumers and businesses of adopting "bleeding edge" communications technology even if it was not yet standardized  HP Pavilion DV6-1210SA battery .

Thus, standards organizations had to put forth standards much faster, or find themselves ratifying de facto standards after the fact.

The ITU-T now operates under much more streamlined processes. The time between an initial proposal of a draft document by a member company and the final approval of a full-status ITU-T Recommendation can now be as short as a few months (or less in some cases)  HP Pavilion DV7 battery .

This makes the standardization approval process in the ITU-T much more responsive to the needs of rapid technology development than in the ITU's historical past. New and updated Recommendations are published on an almost daily basis, and much of the library of over 3,270 Recommendations is now free of charge online  Ibm THINKPAD X200 Battery .

(Specifications jointly maintained by the ITU-T and ISO/IEC are not free. )

ITU-T has moreover tried to facilitate cooperation between the various forums and standard-developing organizations (SDOs). This collaboration is necessary to avoid duplication of work and the consequent risk of conflicting standards in the market place Ibm THINKPAD X200 Battery .

In the work of standardization, ITU-T cooperates with other SDOs, e.g., the International Organization for Standardization (ISO) and the Internet Engineering Task Force (IETF)

Development of Recommendations

Most of the work of ITU-T is carried out by its Sector Members and Associates  Ibm THINKPAD X200 Battery ,

while the Telecommunication Standardization Bureau (TSB) is the executive arm of ITU-T and coordinator for a number of workshops and seminars to progress existing work areas and explore new ones. The events cover a wide array of topics in the field of information and communication technologies (ICT) and attract high-ranking experts as speakers SONY VAIO VGN-FW21E Battery ,

and attendees from engineers to high-level management from all industry sectors.

The technical work, the development of Recommendations, of ITU-T is managed by Study Groups (SGs). The people involved in these SGs are experts in telecommunications from all over the world  Asus M52N Battery .

There are currently 13 SGs. Study groups meet face to face according to a calendar issued by the TSB. SGs are augmented by Focus Groups (FGs), an instrument created by ITU-T, providing a way to quickly react to ICT standardization needs and allowing great flexibility in terms of participation and working methods  Dell Latitude E6400 ATG Battery .

The key difference between SGs and FGs is that the latter have greater freedom to organize and finance themselves, and to involve non-members in their work. Focus Groups can be created very quickly, are usually short-lived and can choose their own working methods, leadership, financing, and types of deliverables  SONY VAIO VGN-FW21J Battery .

Recent examples include work on Next Generation Networking, Internet Protocol Television (IPTV) and digital identity management.

Approval of Recommendations

The “Alternative Approval Process” (AAP) is a fast-track approval procedure that was developed to allow standards to be brought to market in the timeframe that industry now demands  SONY VAIO VGN-FW21L Battery .

This dramatic overhaul of standards-making by streamlining approval procedures was implemented in 2001 and is estimated to have cut the time involved in this critical aspect of the standardization process by 80 to 90 per cent. This means that an average standard which took around four years to approve and publish until the mid nineties  SONY VAIO VGN-FW21M Battery ,

and two years until 1997, can now be approved in an average of two months, or as little as five weeks.

Besides streamlining the underlying procedures involved in the approval process, an important contributory factor to the use of AAP is electronic document handling  SONY VAIO VGN-FW21Z Battery .

Once the approval process has begun the rest of the process can be completed electronically, in the vast majority of cases, with no further physical meetings.

The introduction of AAP also formalizes public/private partnership in the approval process by providing equal opportunities for both Sector Members and Member States in the approval of technical standards  SONY VAIO VGN-FW25T/B Battery .

Once the text of a draft Recommendation prepared by SG experts is considered mature, it is submitted for review to an SG meeting. If agreed by the meeting it is given Consent. This means that the SG has given its consent that the text is sufficiently mature to initiate a final review process leading to approval of the draft Recommendation  SONY VAIO VGN-FW26T/B Battery .

After this Consent has been achieved, TSB announces the start of the AAP procedure by posting the draft text to the ITU-T web site and calling for comments. This gives the opportunity for all members to review the text. This phase, called Last Call, is a four-week period in which comments can be submitted by Member States and Sector Members  SONY VAIO VGN-FW27/B Battery .

If no comments other than editorial corrections are received, the Recommendation is considered approved since no issues were identified that might need any further work. However, if there are any comments, the SG chairman, in consultation with TSB, sets up a comment resolution process by the concerned experts  SONY VAIO VGN-FW27/W Battery .

The revised text is then posted on the web for an Additional Review period of three weeks.

Similar to the Last Call phase, in Additional Review the Recommendation is considered as approved if no comments are received  SONY VAIO VGN-FW31ZJ Battery .

If comments are received, it is apparent that there are some issues that still need more work, and the draft text and all comments are sent to the next Study Group meeting for further discussion and possible approval.

Those Recommendations considered as having policy or regulatory implications are approved through  SONY VAIO VGN-FW27T/H Battery

what is known as the “Traditional Approval Process” (TAP), which allows a longer period for reflection and commenting by Member States. TAP Recommendations are also translated into the six working languages of ITU (Arabic, Chinese, English, French, Russian and Spanish)  SONY VAIO VGN-FW29/B Battery .

Series and Recommendations

ITU-T Recommendations are the names given to telecommunications and computer protocol specification documents published by ITU-T.

Many of the Recommendations that define OSI are also ISO standards  SONY VAIO VGN-FW290JRB Battery .

Standards for Internet protocols are typically developed in the IETF, and standards for mobile telephone systems are developed in ETSI and other forums.

Series of ITU Recommendations

ITU-T issues Recommendations that have names like X.500, where X is the series and 500 is an identifying number  SONY VAIO VGN-FW290JTB Battery .

When a Recommendation is updated, it will (mostly) keep the same number, so the year of issue may be necessary to identify a specific version of a Recommendation. The term "X.500" is used both to refer to the specific X.500 Recommendation, and to the entire family of Recommendations named X.5xx  SONY VAIO VGN-FW290JTH Battery ,

where the specific X.500 Recommendation forms the introduction and overview to the set.

The Working Group on Internet Governance (WGIG) was a United Nations multistakeholder Working group initiated after the 2003 World Summit on the Information Society (WSIS) first phase Summit in Geneva to agree on the future of Internet governanceSONY VAIO VGN-FW33G/E1 Battery.

The first phase of World Summit on the Information Society (WSIS) agreed to continue the dialogue on Internet Governance in the Declaration of Principles and Action Plan adopted on 12 December 2003, to prepare for a decision at the second phase of the WSIS in Tunis during November 2005  SONY VAIO VGN-FW33G/W Battery .

In this regard, the first phase of the Summit requested the United Nations Secretary-General to establish a Working Group on Internet Governance (WGIG). The WGIG was asked to present the result of its work in a report "for consideration and appropriate action" for the second phase of the WSIS in Tunis 2005  SONY VAIO VGN-FW33GW Battery .

The main activity of the WGIG was "to investigate and make proposals for action, as appropriate, on the governance of Internet by 2005." The WGIG was asked to present the result of its work in a report "for consideration and appropriate action for the second phase of the WSIS in Tunis 2005."  Dell XPS M1210 Battery

It was asked, inter alia, to deal with the following issues:

- Develop a working definition of Internet Governance;

- Identify the public policy issues that are relevant to Internet Governance  http://www.hdd-shop.co.uk;

- Develop a common understanding of the respective roles and responsibilities of governments, existing international organizations and other forums as well as the private sector and civil society from both developing and developed countries.

A few weeks before the release of the WGIG Report the U.S  Dell KM958 battery .

reiterated its claim of ICANN and stated that it wished to "maintain its historic role in authorizing changes or modifications to the authoritative root zone file"  .


The chair of WGIG was Nitin Desai, and the executive coordinator was Markus Kummer  Dell Studio 1555 battery .

The 40 official members are listed in the final report; in addition, there were many people attending the meetings to contribute their views.

View of Internet governance

The report of the WGIG divided Internet Governance into four sections  Sony VGP-BPS13 battery :

  • Infrastructure (mainly the Domain Name System and IP addresses)
  • Internet issues such as security, safety and privacy (including spam and cybercrime)
  • Intellectual property and international trade (including copyrights)  Sony VGP-BPS13/B battery
  • Development Issues (particularly developing countries)


Four options for the management of Internet-related public policy issues were proposed in the Final Report of the WGIG Sony VGP-BPS13/S battery ,

finalised during their fourth meeting, and presented to stakeholders on 18 July 2005 in preparation for the November 2005 meeting in Tunis, Tunisia. These proposals all include the introduction of an open Multi-stakeholder based Internet Governance forum to give greater influence to the stakeholders around the world, including civil society Sony VGP-BPS13A/B battery ,

private sector and governments. Each model also included different strategies for the oversight role, currently held by the United States Department of Commerce.

The proposed models were:  Sony VGP-BPS13B/B battery

  1. Create the Global Internet Council (GIC) consisting of governments and involved stakeholders to assume the U.S. oversight role of ICANN.
  2. Ensure that ICANNs Governmental Advisory Committee is an official forum for debate, strengthening its position by allowing for the support of various governments  Sony VGP-BPL9 battery .
  3. Remove the U.S. oversight of ICANN and restrict it to the narrow technical role, forming the International Internet Council (IIC) to manage most aspects of the Internet administration.
  4. Create three new bodies:  Sony VGP-BPS13B/B battery
    • The Global Internet Policy Council (GIPC) to manage "internet-related public policy issues"
    • The World Internet Corporation for Assigned Names and Numbers (WICANN) to take over from ICANN
    • The Global Internet Governance Forum (GIGF), a central debating forum for governments Sony VGP-BPL15 battery .


Some critics have hinted that the idea that the world's countries require a more "equal" say in Internet governance, masks the desire by some governments to conduct censorship or monitor their citizens more effectively (EFF on Internet Governance)  Dell Inspiron E1505 battery .

Fears that increased "governance" will bring with it more regulation and fees have been expressed. IT experts have expressed doubts that a U.N. body that does not necessarily know enough about the Internet will effectively coordinate the Internet technologicallyHP Pavilion dv6000 Battery .

The director of ICANN has expressed concerns that some of the changes proposed represent a government-focused "top-down" philosophy, and that this is incompatible with the current "bottom-up" structure of the Internet mandated by US policy  HP Pavilion dv8000 battery .

The U.S Government's negotiating position in Tunis Prepcom 3 was flexible on the principle of global involvement, very strong on the principle of multistakeholder participation, but inflexible on the need for US control to remain for the foreseeable future in order to ensure the "security and stability of the Internet"  HP PAVILION DV6000 Battery .

This generally showed itself in U.S. support for proposals allowing other governments to have a larger role in the management of their ccTLDs, but no change to the management or control of the root zone file.

The majority of stakeholders want to avoid a politicisation of the Internet  HP PAVILION DV8000 Battery ,

and some consider the effort of the WGIG as launching a set of alien and dangerous terms and ideas. Others believe that it has been an important forum for discussion of the often contentious issue of Internet Governance, as well as a model for multistakeholder cooperation  SONY VAIO VGN-FZ Battery .

Some feel that either of the alternatives is better: a division of the Internet or a defense of the status quo. The United States has traditionally considered its function as a defender of citizens' rights worldwide, which is one reason it wants to keep the Internet free for private individuals rather than overly regulated by governments or international organisations   HP Pavilion DV6000 battery .

Some of the options presented in the WGIG Report may be seen by some as too government-oriented, while one option reflects the status quo, and may be seen as being too US-centric  HP Pavilion DV8000 battery .

The final agreements reached in Tunis The Tunis Agenda (paras 29-82 concern Internet Governance) and the Tunis Commitment include the formation of the Internet Governance Forum. No agreement was reached on the oversight function  HP Pavilion DV6000 battery .

Broadcast-safe video (broadcast legal or legal signal) is a term used in the broadcast industry to define video and audio compliant with the technical or regulatory broadcast requirements of the target area or region the feed might be broadcasting to   HP Pavilion DV8000 battery .

In the United States, the Federal Communications Commission (FCC) is the regulatory authority; in most of Europe, standards are set by theEuropean Broadcasting Union (EBU)  SONY VAIO VGN-FZ18 Battery .

Broadcast safe audio

Broadcast engineers in North America usually line up their audio gear to nominal reference level of 0 dB on a VU meter aligned to +4dBu or -20dBFs, in Europe equating to roughly +4 dBm or -18dBFS. Peak signal levels must not exceed the nominal level by more than +10dB   SONY VAIO VGN-FZ21E Battery .

Broadcast audio as a rule must be as free as possible of Gaussian noise, that is to say, it must be as close to the noise floor, as is reasonably possible, considering the storage or transmission medium  SONY VAIO VGN-FW31J Battery .

Broadcast audio must have a good signal-to-noise ratio, where speech or music is a bare minimum of 16db above the noise of the recording or transmission system. For audio that has a much poorer signal-to-noise ratio (like cockpit voice recorders), sonic enhancement is recommended  SONY VAIO VGN-FW31J Battery .

Non-Standard Video

Although almost any video gear can create problems when broadcast, equipment aimed at consumers sometimes produces video signals which are not broadcast safe   SONY VAIO VGN-FW21E Battery .

Usually this is to reduce the cost of the gear, since a non-standard video signal in the home might not create the problems that one might find in a broadcast facility. Potential flaws exist with  SONY VAIO VGN-NR11S/S Battery:

  • VHS and 8 mm : Consumer devices generally lack time base correction that may cause problems with genlock and sync with some analogue and digital broadcast equipment. Consumer analogue video systems have greater system noise and lower chrominance and luminace than is normal for standard definition TV  SONY VAIO VGN-NR11M/S Battery .
  • As a general broadcast engineering rule all analogue videotape origin material should be genlocked before transmission, but this is not mandatory or necessary for all conditions. All analogue videotape by default is broadcast safe under normal playing conditions  SONY VAIO VGN-NR11Z/S Battery .
  • Older videogame systems : Before the sixth generation of videogame consoles, most videogames generated a video signal lacking the half scan line needed to make interlace happen. This subtle simplification caused NTSC sets to scan 240p/60 instead of 480i/60, with similar results for PAL  SONY VAIO VGN-NR11Z/T Battery .
  • While this actually improved picture quality for the kind of images that videogames of this era generated, such a signal modification could cause problems in a broadcast environment as the signal behaviour is outside the original television system specifications  Sony VAIO VGN-FZ21E Battery .
  • Genlocking -- but not timebase correction -- are the recommended broadcast engineering solutions.
  • Computer video signals : Computer video can be set up to run at many different frame or field rates, ranging 50 FPS to more than 240 FPS  Sony VAIO VGN-FW21E Battery .
  • Computer video is generally progressive by default, but many interlaced modes exist. A "Scanrate Converter" is typically needed to convert these signals to one the many acceptable broadcast standards, such as 59.97 hz or 50 hz  Sony VAIO VGN-NR11S/S Battery .
  • This type of conversion typically degrades the quality of the broadcast image, usually resulting with either "motion artifacts" or a lower resolution. It is recommended that the display rate be set to equal the target television rate if possible  Sony VAIO VGN-NR11Z/S Battery .

In digital television only environments

In nations that have fully converted to digital television, broadcast safe analogue television takes on a slightly different meaning. All broadcasting systems will have been mostly converted to digital only outputs, leaving fewer entry points for analogue television signals  Sony VAIO VGN-NR11M/S Battery .

What this means is that all devices that feed to the television transmitter must take in and feed standard analogue television signals into the transmission chain. Mostly it is up to the switcher to notify if there is non-broadcast safe video to the programmer  Sony VAIO VGN-NR11Z/T Battery .

However, due to the limitations of many switchers for DTV and HDTV it ultimately is up to the automation systems to alert the programmer of non-broadcast safe video inputs.

As a matter of broadcast engineering practice, 4:3 analogue television signals will always pose the most problems with broadcast safe compliance  SONY VAIO VGN-FZ180E Battery .

The use of portable and cheap timebase-genlock systems for analogue television inputs in the digital television studio will be clearly mandatory for the next 50 years.

Serial digital interface (SDI) is a family of video interfaces standardized by SMPTE  SONY VAIO VGN-FZ220E Battery .

For example, ITU-R BT.656 and SMPTE 259M define digital videointerfaces used for broadcast-grade video. A related standard, known as high-definition serial digital interface (HD-SDI), is standardized in SMPTE 292M; this provides a nominal data rate of 1.485 Gbit/s   SONY VAIO VGN-FZ340E Battery .

An emerging interface, commonly known in the industry as dual link HD-SDI and consisting essentially of a pair of SMPTE 292M links, is standardized inSMPTE 372M; this provides a nominal 2.970 Gbit/s interface used in applications (such as digital cinema or HDTV 1080P) that require greater fidelity and resolution than standard HDTV can provide SONY VAIO VGN-FZ460E Battery .

A more recent interface, 3G-SDI, consisting of a single 2.970 Gbit/s serial link, is standardized in SMPTE 424Mthat will replace the dual link HD-SDI.

These standards are used for transmission of uncompressed, unencrypted digital video signals (optionally including embedded Audio and/or Time Code) within television facilities  SONY VAIO VGN-FZ480E Battery ;

they can also be used for packetized data. Coaxial variants of the specification range in length but are typically less than 300 meters. Fiber optic variants of the specification such as 297M allow for long-distance transmission limited only by maximum fiber length and/or repeaters   SONY VAIO VGN-FZ4000 Battery .

SDI and HD-SDI are currently only available in professional video equipment; various licensing agreements, restricting the use of unencrypted digital interfaces to professional equipment, prohibit their use in consumer equipment  SONY VAIO VGN-FZ31E Battery.

There are various mod kits for existing DVD players and other devices, which allow a user to add a serial digital interface to these devices.

Electrical interface

The various serial digital interface standards all use (one or more) coaxial cables with BNC connectors, with a nominal impedance of 75 ohms  SONY VAIO VGN-FZ31B Battery .

This is the same type of cable used in analog video setups, which potentially makes for easier upgrades (though higher quality cables may be necessary for long runs at the higher bitrates). The specified signal amplitude at the source is 800 mV (±10%) peak-to-peak; far lower voltages may be measured at the receiver owing to attenuation  SONY VAIO VGN-FZ31J Battery .

Using equalisation at the receiver, it is possible to send 270 Mbit/s SDI over 300 metres without use of repeaters , but shorter lengths are preferred. The HD bitrates have a shorter maximum run length, typically 100 meters .

Uncompressed digital component signals are transmitted  SONY VAIO VGN-FZ31M Battery .

Data is encoded in NRZI format, and a linear feedback shift register is used to scramble the data to reduce the likelihood that long strings of zeroes or ones will be present on the interface. The interface is self-synchronizing and self-clocking  SONY VAIO VGN-FZ31Z Battery .

Framing is done by detection of a special synchronization pattern, which appears on the (unscrambled) serial digital signal to be a sequence of ten ones followed by twenty zeroes (twenty ones followed by forty zeroes in HD); this bit pattern is not legal anywhere else within the data payload  SONY VAIO VGN-FZ38M Battery .

Bit rates

Several bit rates are used in serial digital video Signal:

  • For standard definition applications, as defined by SMPTE 259M, the possible bit rates are 270 Mbit/s, 360 Mbit/s, 143 Mbit/s, and 177 Mbit/s. 270 Mbit/s is by far the most commonly used  SONY VGP-BPS8 Battery ;
  • though the 360 Mbit/s interface (used for widescreen standard definition) is sometimes encountered. The 143 and 177 Mbit/s interfaces were intended for transmission of composite-encoded (NTSC or PAL) video digitally, and are now considered obsolete  SONY VGP-BPS13/S Battery .
  • For enhanced definition applications (mainly 525P), there are several 540 Mbit/s interfaces defined, as well as an interface standard for a dual-link 270 Mbit/s interface. These are rarely encountered.
  • For HDTV applications, the serial digital interface is defined by SMPTE 292M  SONY VGP-BPS13A/B Battery .
  • Two bit rates are defined, 1.485 Gbit/s, and 1.485/1.001 Gbit/s. The factor of 1/1.001 is provided to allow SMPTE 292M to support video formats with frame rates of 59.94 Hz, 29.97 Hz, and 23.98 Hz, in order to be compatible with existing NTSC systems  SONY VGP-BPS13B/B Battery .
  • The 1.485 Gbit/s version of the standard supports other frame rates in widespread use, including 60 Hz, 50 Hz, 30 Hz, 25 Hz, and 24 Hz. It is common to collectively refer to both standards using a nominal bit rate of 1.5 Gbit/s   SONY VGP-BPS13A/S Battery .
  • For very high-definition applications, requiring greater resolution, frame rate, or color fidelity than the HD-SDI interface can provide, the SMPTE 372M standard defines the dual link interface. As the name suggests, this interface consists of two SMPTE 292M interconnects operating in parallel   SONY VGP-BPS13AS Battery .
  • In particular, the dual link interface supports 10-bit, 4:2:2, 1080P formats at frame rates of 60 Hz, 59.94 Hz, and 50 Hz, as well as 12-bit color depth, RGB encoding, and 4:4:4 colour sampling   Dell Inspiron 1320n Battery .
  • A nominal 3 Gbit/s interface (more accurately, 2.97 Gbit/s, but commonly referred to as "3 gig") is standardized by SMPTE; as of June 2006, chipsets for this interface are just becoming available. It is intended to support all of the features supported by the dual 1.485 Gbit/s interface, but requires only one cable rather than two  Dell Studio 1450 Battery .

Other interfaces

SMPTE 292M defines an optical interface as well as an electrical one; this interface is widely considered to be obsolete. An 8-bit parallel digital interface is defined by ITU-R Rec. 601; this is also obsolete (however, many clauses in the various standards accommodate the possibility of an 8-bit interface)  Dell Studio 1457 Battery .

Data Format

In SD and ED applications, the parallel data format is defined to 10 bits wide, whereas in HD applications, it is 20 bits wide, divided into two parallel 10-bit datastreams (known as Y and C). The SD datastream is arranged like this  Dell Latitude D610 Battery :

Cb Y Cr Y' Cb Y Cr Y'

whereas the HD datastreams are arranged like this:

Y Y' Y Y' Y Y' Y Y'  Toshiba NB100 Battery ;Dell Latitude D610 Battery
Cb Cr Cb Cr Cb Cr Cb Cr

For all serial digital interfaces (excluding the obsolete composite encodings), the native color encoding is 4:2:2 YCbCr format. The luminance channel (Y) is encoded at full bandwidth (13.5 MHz in 270 Mbit/s SD, ~75 MHz in HD)  Toshiba Satellite M65 battery ,

and the two chrominance channels (Cb and Cr) are subsampled horizontally, and encoded at half bandwidth (6.75 MHz or 37.5 MHz). The Y, Cr, and Cb samples are co-sited (acquired at the same instance in time), and the Y' sample is acquired at the time halfway between two adjacent Y samples  Toshiba Satellite M60 battery .

In the above, Y refers to luminance samples, and C to chrominance samples. Cr and Cb further refer to the red and blue "color difference" channels; see Component Video for more information. This section only discusses the native color encoding of SDI; other color encodings are possible by treating the interface as a generic 10-bit data channel  Dell Latitude D830 Battery .

The use of other colorimetry encodings, and the conversion to and from RGB colorspace, is discussed below.

Video payload (as well as ancillary data payload) may use any 10-bit word in the range 4 to 1019 (004 to 3FB in hexadecimal) Dell Latitude D620 Battery

inclusive; the values 0-3 and 1020-1023 (3FC - 3FF) are reserved and may not appear anywhere in the payload. These reserved words have two purposes; they are used both for Synchronization packets and for Ancillary data headers  Dell Inspiron Mini 10 Battery .

Synchronization packets

A synchronization packet (commonly known as the timing reference signal or TRS) occurs immediately before the first active sample on every line, and immediately after the last active sample (and before the start of the horizontal blanking region)  Sony VGN-FW11S Battery .

The synchronization packet consists of four 10-bit words, the first three words are always the same--0x3FF, 0, 0; the fourth consists of 3 flag bits, along with an error correcting code. As a result, there are 8 different synchronization packets possible  Sony VGN-FW11M Battery .

In the HD-SDI and dual link interfaces, synchronization packets must occur simultaneously in both the Y and C datastreams. (Some delay between the two cables in a dual link interface is permissible; equipment which supports dual link is expected to buffer the leading link in order to allow the other link to catch up)  Sony VGN-FW139E/H battery .

In SD-SDI and enhanced definition interfaces, there is only one datastream, and thus only one synchronization packet at a time. Other than the issue of how many packets appear, their format is the same in all versions of the serial-digital interface  Dell Latitude E5400 Battery .

The flags bits found in the fourth word (commonly known as the XYZ word) are known as H, F, and V. The H bit indicates the start of horizontal blank; and synchronization bits immediately preceding the horizontal blanking region must have H set to one. Such packets are commonly referred to as End of Active Video, or EAV packets  Dell Latitude E4200 Battery .

Likewise, the packet appearing immediately before the start of the active video has H set to 0; this is the Start of Active Videoor SAV packet.

Likewise, the V bit is used to indicate the start of the vertical blanking region  Dell Inspiron 300M Battery ;

an EAV packet with V=1 indicates the following line (lines are deemed to start at EAV) is part of the vertical interval, an EAV packet with V=0 indicates the following line is part of the active picture.

The F bit is used in interlaced and segmented-frame formats to indicate whether the line comes from the first or second field (or segment). In progressive scan formats, the F bit is always set to zero  Dell Studio 1737 battery .

Line counter and CRC

In the high definition serial digital interface (and in dual-link HD), additional check words are provided to increase the robustness of the interface. In these formats, the four samples immediately following the EAV packets (but not the SAV packets) contain a cyclic redundancy check field, and a line count indicator   Dell Inspiron E1505 battery .

The CRC field provides a CRC of the preceding line (CRCs are computed independently for the Y and C streams), and can be used to detect bit errors in the interface. The line count field indicates the line number of the current line.

The CRC and line counts are not provided in the SD and ED interfaces   Dell RM791 battery .

Instead, a special ancillary data packet known as an EDH packet may be optionally used to provide a CRC check on the data.

Line and sample numbering

Each sample within a given datastream is assigned a unique line and sample number   Toshiba Satellite P10 Battery .

In all formats, the first sample immediately following the SAV packet is assigned sample number 0; the next sample is sample 1; all the way up to the XYZ word in the following SAV packet. In SD interfaces, where there is only one datastream, the 0th sample is a Cb sample   Acer Aspire One battery 10400mAh ;

the 1st sample a Y sample, the 2nd sample a Cr sample, and the third sample is the Y' sa

mple; the pattern repeats from there. In HD interfaces, each datastream has its own sample numbering--so the 0th sample of the Y datastream is the Y sample, the next sample the Y' sample, etc   Dell Precision M70 Battery .

Likewise, the first sample in the C datastream is Cb, followed by Cr, followed by Cb again.

Lines are numbered sequentially, starting from 1, up to the number of lines per frame of the indicated format (typically 525, 625, 750, or 1125)   SONY VGN -FZ210CE Battery .

Determination of line 1 is somewhat arbitrary; however it is unambiguously specified by the relevant standards. In 525-line systems, the first line of vertical blank is line 1, whereas in other interlaced systems (625 and 1125-line), the first line after the F bit transitions to zero is line 1  Toshiba Satellite L305 Battery .

Note that lines are deemed to start at EAV, whereas sample zero is the sample following SAV. This produces the somewhat confusing result that the first sample in a given line of 1080i video is sample number 1920 (the first EAV sample in that format), and the line ends at the following sample 1919 (the last active sample in that format)  Toshiba Satellite T4900 Battery  .

Note that this behavior differs somewhat from analog video interfaces, where the line transition is deemed to occur at the sync pulse, which occurs roughly halfway through the horizontal blanking region.

Link numbering

Link numbering is only an issue in dual-link interfaces   Toshiba PA3399U-2BRS battery .

The first link (the primary link), is assigned a link number of 1, subsequent links are assigned increasing link numbers; so the second (secondary) link in a dual-link system is link 2. The link number of a given interface is indicated by a VPID packet located in the vertical ancillary data space  Sony VGP-BPS10 battery .

Note that the data layout in dual link is designed so that the primary link can be fed into a single-link interface, and still produce usable (though somewhat degraded) video. The secondary link generally contains things like additional LSBs (in 12-bit formats)  Sony VGP-BPS9 battery ,

non-cosited samples in 4:4:4 sampled video (so that the primary link is still valid 4:2:2), and alpha or data channels. If the second link of a 1080P dual link configuration is absent, the first link still contains a valid 1080i signal.

In the case of 1080p60, 59.94, or 50 Hz video over a dual link; each link contains a valid 1080i signal at the same field rate  Sony VGP-BPS11 battery .

The first link contains the 1st, 3rd, and 5th lines of odd fields and the 2nd, 4th, 6th, etc. lines of even fields, and the second link contains the even lines on the odd fields, and the odd lines on the even fields. When the two links are combined, the result is a progressive-scan picture at the higher frame rate  Sony VGP-BPS22 battery .

Ancillary data

Like SMPTE 259M, SMPTE 292M supports the SMPTE 291M standard for ancillary data. Ancillary data is provided as a standardized transport for non-video payload within a serial digital signal  Sony VGP-BPL8 battery ;

it is used for things such as embedded audio, closed captions, timecode, and other sorts of metadata. Ancillary data is indicated by a 3-word packet consisting of 0, 3FF, 3FF (the opposite of the synchronization packet header), followed by a two-word identification code, a data count word (indicating 0 - 255 words of payload)  Sony VGP-BPS14 battery ,

the actual payload, and a one-word checksum. Other than in their use in the header, the codes prohibited to video payload are also prohibited to ancillary data payload.

Specific applications of ancillary data include embedded audio, EDH, VPID and SDTI  Sony VGP-BPS21 battery .

In dual link applications; ancillary data is mostly found on the primary link; the secondary link is to be used for ancillary data only if there is no room on the primary link. One exception to this rule is the VPID packet; both links must have a valid VPID packet present  Toshiba Satellite A200 Battery .

Embedded audio

Both the HD and SD serial interfaces provide for 16 channels of embedded audio. The two interfaces use different audio encapsulation methods - SD uses the SMPTE 272M standard, whereas HD uses the SMPTE 299M standard  Toshiba Satellite 1200 Battery .

In either case, an SDI signal may contain up to sixteen audio channels (8 pairs) embedded 48 kHz, 24-bit audio channels along with the video. Typically, 48 kHz, 24-bit (20-bit in SD) PCM audio is stored, in a manner directly compatible with the AES3 digital audio interface  Toshiba Satellite M300 Battery .

These are placed in the (horizontal) blanking periods, when the SDI signal carries nothing useful, since the receiver generates its own blanking signals from the TRS.

In dual-link applications, 32 channels of audio are available, as each link may carry 16 channels  SONY VGP-BPS13A/Q Battery .


As the standard definition interface carries no checksum, CRC, or other data integrity check, an EDH (Error Detection and Handling) packet may be optionally placed in the vertical interval of the video signal  SONY VGP-BPS13A/Q Battery .

This packet includes CRC values for both the active picture, and the entire field (excluding those lines at which switching may occur, and which should contain no useful data); equipment can compute their own CRC and compare it with the received CRC in order to detect errors   SONY VGP-BPS13B/Q Battery .

EDH is typically only used with the standard definition interface; the presence of CRC words in the HD interface make EDH packets unnecessary.


VPID (or video payload identifier) packets are increasingly used to describe the video format  SONY VGP-BPS13B/Q Battery .

In early versions of the serial digital interface, it was always possible to uniquely determine the video format by counting the number of lines and samples between H and V transitions in the TRS. With the introduction of dual link interfaces, and segmented-frame standards, this is no longer possible   SONY VGP-BPS13/Q Battery ;

thus the VPID standard (defined by SMPTE 352M) provides a way to uniquely and unambiguously identify the format of the video payload.

Video payload and blanking

The active portion of the video signal is defined to be those samples which follow an SAV packet, and precede the next EAV packetSONY VGP-BPS13/Q Battery ;

where the corresponding EAV and SAV packets have the V bit set to zero. It is in the active portion that the actual image information is stored.

Color encoding

Several color encodings are possible in the serial digital interface. The default (and most common case) is 10-bit linearly sampled video data encoded as 4:2:2 YCbCr  SONY VGP-BPS21A/B Battery .

(YCbCr is a digital representation of the YPbPr colorspace). Samples of video are stored as described above. Data words correspond to signal levels of the respective video components, as follows  SONY VGP-BPS21/S Battery :

  • The luminance (Y) channel is defined such that a signal level of 0 mV is assigned the codeword 64 (40 hex), and 700 millivolts (full scale) is assigned the codeword 940 (3AC hex) .
  • For the chroma channels, 0 mV is assigned the code word 512 (200 hex), -350mV is assigned a code word of 64 (40 hex), and +350mV is assigned a code word of 960 (3C0 hex)  SONY VGP-BPS21B Battery .

Note that the scaling of the luma and chroma channels is not identical. The minimum and maximum of these ranges represent the preferred signal limits, though the video payload may venture outside these ranges (providing that the reserved code words of 0 - 3 and 1020 - 1023 are never used for video payload)  SONY VGP-BPS21A Battery .

In addition, the corresponding analog signal may have excursions further outside of this range.


As YPbPr (and YCbCr) are both derived from the RGB colorspace, a means of converting is required. There are three colorimetries typically used with digital video   SONY VGP-BPS21 Battery :

  • SD and ED applications typically use a colorimetry matrix specified in ITU-R Rec. 601.
  • Most HD, dual link, and 3Gb applications use a different matrix, specified in ITU-R Rec. 709  Sony VGP-BPS21A/B Battery .
  • The 1035-line HD standards specified by SMPTE 260M (primarily used in Japan and now largely considered obsolete), used a colorimetry matrix specified by SMPTE 240M. This colorimetry is nowadays rarely used, as the 1035-line formats have been superseded by 1080-line formats  Sony VGP-BPS21/S Battery .

Other color encodings

The dual-link and 3 Gbit/s interfaces additionally support other color encodings besides 4:2:2 YCbCr, namely:

  • 4:2:2 and 4:4:4 YCbCr, with an optional alpha (used for chroma keying) or data (used for non-video payload) channel
  • 4:4:4 RGB, also with an optional alpha or data channel  Sony VGP-BPS21A Battery
  • 4:2:2 YCbCr, 4:4:4 YCbCr, and 4:4:4 RGB, with 12 bits of color information per sample, rather than 10. Note that the interface itself is still 10 bit; the additional 2 bits per channel are multiplexed into an additional 10-bit channel on the second link Sony VGP-BPS21 Battery .

If an RGB encoding is used, the three primaries are all encoded in the same fashion as the Y channel; a value of 64 (40 hex) corresponds to 0mV, and 940 (3AC hex) corresponds to 700mV

12-bit applications are scaled in a similar fashion to their 10-bit counterparts; the additional two bits are considered to be LSBs Sony Vaio PCG-5G2L Battery .

Vertical and horizontal blanking regions

For portions of the vertical and horizontal blanking regions which are not used for ancillary data, it is recommended that the luma samples be assigned the code word 64 (40 hex), and the chroma samples be assigned 512 (200 hex); both of which correspond to 0 mV   Sony Vaio PCG-5G3L Battery .

It is permissible to encode analog vertical interval information (such as vertical interval timecode or vertical interval test signals) without breaking the interface, but such usage is nonstandard (and ancillary data is the preferred means for transmitting metadata)  Sony Vaio PCG-5J1L Battery .

Conversion of analog sync and burst signals into digital, however, is not recommended--and neither is necessary in the digital interface.

Supported video formats

The various versions of the serial digital interface support numerous video formats  Sony Vaio PCG-5K2L Battery .

  • The 270 Mbit/s interface supports 525-line, interlaced video at a 59.94 Hz field rate (29.97 Hz frame rate), and 625-line, 50 Hz interlaced video. These formats are highly compatible with NTSC andPAL-B/G/D/K/I systems respectively; and the terms NTSC and PAL are often (incorrectly) used to refer to these formats   Sony Vaio PCG-5J2L Battery .
  • (NTSC and PAL are composite color encoding schemes; and the serial digital interface--other than the obsolete 143 Mbit/s and 177 Mbit/s forms, is a component standard).
  • The 360 Mbit/s interface supports 525i and 625i widescreen   Sony Vaio PCG-5K1L Battery .
  • It can also be used to support 525p, if 4:2:0 sampling is used.
  • The various 540 Mbit/s interfaces support 525p and 625p formats.
  • The nominal 1.5 Gbit/s interfaces support most high definition formats   Sony Vaio PCG-6S2L Battery .
  • Supported formats include 1080/60i, 1080/59.94i, 1080/50i, 1080/30p, 1080/29.97p, 1080/25p, 1080/24p, 1080/23.98p, 720/60p, 720/59.94p, and 720/50p. In addition, there are several 1035i formats (an obsolete Japanese television standard)   Sony Vaio PCG-6S3L Battery ,
  • half-bandwidth 720p standards such as 720/24p (used in some film conversion applications, and unusual because it has an odd number of samples per line ), and various 1080psf (progressive, segmented frame) formats. Progressive Segmented frames formats appear as interlace video but contain video which is progressively scanned  Sony Vaio PCG-6V1L Battery .
  • This is done to support analog monitors and televisions, many of which are incapable of locking to low field rates such as 30 Hz and 24 Hz.
  • The dual link HD interface supports 1080/60p, 1080/59.94p  Sony Vaio PCG-6W1L Battery ,
  • and 1080/50p, as well as 4:4:4 encoding, greater color depth, RGB encoding, alpha channels, and nonstandard resolutions (often encountered in computer graphics or digital cinema).

Related interfaces

In addition to the regular serial digital interface described here, there are several other similar interfaces which are similar to, or are contained within, a serial digital interface.


There is an expanded specification called SDTI (Serial Data Transport Interface), which allows compressed  Sony Vaio PCG-6W2L Battery

(i.e. DV, MPEG and others) video streams to be transported over an SDI line. This allows for multiple video streams in one cable or faster-than-realtime (2x, 4x,...) video transmission. A related standard, known as HD-SDTI, provides similar capability over an SMPTE 292M interface  Sony Vaio PCG-6W3L Battery .

The SDTI interface is specified by SMPTE 305M. The HD-SDTI interface is specified by SMPTE 348M.


The standard SMPTE 349M: Transport of Alternate Source Image Formats through SMPTE 292M, specifies a means to encapsulate non-standard and lower-bitrate video formats within an HD-SDI interface  Sony Vaio PCG-7111L Battery .

This standard allows, for example, several independent standard definition video signals to be multiplexed onto an HD-SDI interface, and transmitted down one wire. This standard doesn't merely adjust EAV and SAV timing to meet the requirements of the lower-bitrate formats   Sony Vaio PCG-7112L Battery ;

instead, it provides a means by which an entire SDI format (including synchronization words, ancillary data, and video payload) can be encapsulated and transmitted as ordinary data payload within a 292M stream.

Coordinated Universal Time (abbreviated UTC)  is the time standard by which the world regulates clocks and time  Sony Vaio PCG-7113L Battery .

Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose.

Coordinated Universal Time is a time standard based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the Earth's slowing rotation    Sony Vaio PCG-7133L Battery .

Leap seconds are used to allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich.

Since the difference between UTC and UT1 is not allowed to exceed 0.9 seconds, if high precision is not required, the general term Universal Time (UT) may be used   Sony Vaio PCG-7Z2L Battery .

In casual use, when fractions of a second are not important, Greenwich Mean Time (GMT) can be considered equivalent to UTC or UT1. Saying "GMT" often implies either UTC or UT1 when used within informal or casual contexts. In technical contexts, usage of "GMT" is avoided; the unambiguous terminology "UTC" or "UT1" is preferred.  Sony Vaio PCG-8Y1L Battery

Time zones around the world can be expressed as positive or negative offsets from UTC as in this list; UTC replaced GMT as the basis for the main reference time scale or civil time in various regions on 1 January 1972.


UTC is the time standard used for many Internet and World Wide Web standards    Sony Vaio PCG-8Y2L Battery .

In particular, the Network Time Protocol, which is designed to synchronise the clocks of many computers over the Internet (usually to that of a known accurate atomic clock), uses UTC.

Those who transmit on the amateur radio bands often log the time of their radio contacts in UTC, as transmissions can go worldwide on some frequencies   Sony Vaio PCG-8Z1L Battery .

In the past, the FCC required all amateur radio operators in the United States to log their radio conversations. International broadcasters such as the BBC World Service also use UTC when publishing their schedules and announcing times during broadcasts  Sony Vaio PCG-8Z2L Battery .

UTC is also the time standard used in aviation.  Weather forecasts, flight plans, air traffic control clearances, and maps all use UTC (also colloquially referred to as "Zulu Time", particularly in the United States military) to avoid confusion about time zones and daylight saving time   SONY VAIO VGN-FW31J Battery .


The notation for Coordinated Universal Time is UTC. The International Telecommunication Union and the International Astronomical Union wanted Coordinated Universal Time to have the same notation in all languages    SONY VAIO VGN-FW31E Battery .

English and Frenchspeakers wanted the initials of both their respective language's terms to be used internationally: "CUT" for "coordinated universal time" and "TUC" for "temps universel coordonné". This resulted in the final compromise of "UTC", which conforms to the pattern for the notations of the variants of Universal Time (UT0, UT1, UT2, UT1R etc.)  SONY VAIO VGN-FW31B Battery .


As a time scale, UTC divides up time into days, hours, minutes and seconds. Days are conventionally identified using the Gregorian calendar, but Julian day numbers can also be used. Each day contains 24 hours and each hour contains 60 minutes, but the number of seconds in a minute can be 60, or sometimes 61 or 59  SONY VAIO VGN-FW31M Battery .

Thus, in the UTC time scale, the second and all smaller time units (millisecond, microsecond etc.) are of constant duration, but the minute and all larger time units (hour, day, week etc.) are of variable duration.

Most UTC days contain exactly 86,400 SI seconds, with exactly 60 seconds in each minute    SONY VAIO VGN-FW31Z Battery .

However, since the mean solar day is slightly longer than 86,400 SI seconds, occasionally the last minute of a UTC day will have 61 seconds. The extra second is called a leap second. It accounts for the grand total of the extra length (about 2 milliseconds each) of all the mean solar days since the previous leap second    SONY VAIO VGN-FW38M Battery .

The last minute of a UTC day is allowed to contain 59 seconds to cover the remote possibility of the Earth rotating faster, but that has not yet been necessary since UTC was introduced. The irregular day lengths mean that fractional Julian days do not work properly with UTC   SONY VAIO VGN-AW41JF Battery .

UTC is derived from International Atomic Time (TAI), which is a coordinate time scale tracking notional proper time on the rotating surface of the Earth (the geoid). At any particular time, UTC proceeds as a linear function of TAI. From 1972 onwards, UTC ticks at the same rate as TAI, but earlier (back to the 1961 start of UTC), UTC ticked at a different rate  SONY VAIO VGN-AW41JF/H Battery .

In order to maintain a close approximation to UT1 (equivalent to GMT before 1960), UTC occasionally has discontinuities where it changes from one linear function of TAI to another. These discontinuities take the form of leaps implemented by a UTC day of irregular length, and (prior to 1972) changes to the rate at which UTC ticks relative to TAI  SONY VAIO VGN-AW41MF Battery .

Discontinuities in UTC have occurred only at the end of a Gregorian month.

The International Earth Rotation and Reference Systems Service (IERS) tracks and publishes the difference between UTC and Universal Time, DUT1 = UT1 ? UTC, and introduces discontinuities into UTC to keep DUT1 in the interval (?0.9 s, +0.9 s)  SONY VAIO VGN-AW41MF/H Battery .

Since 1972 the discontinuities have consisted only of a leap of one second at the end of 30 June or 31 December. The IERS publishes its decision on whether to have a leap second on each of these dates a few months in advance, in Bulletin C. In principle, leap seconds can also occur on 31 March or 30 September, but the IERS has never found this necessary  SONY VAIO VGN-FW30B Battery .

As with TAI, UTC is only known with the highest precision in retrospect. The International Bureau of Weights and Measures (BIPM) publishes monthly tables of differences between canonical TAI/UTC and TAI/UTC as estimated in real time by participating laboratories. (See the article on International Atomic Time for details.)  SONY VAIO VGN-FW50B Battery

Because of time dilation, a standard clock not on the geoid, or in rapid motion, will not maintain synchronicity with UTC. Therefore, telemetry from clocks with a known relation to the geoid is used to provide UTC when required, on locations such as those of spacecraft  SONY VAIO VGN-FW51B/W Battery .

UTC is a discontinuous timescale, so it is not possible to compute the exact time interval elapsed between two UTC timestamps without consulting a table that describes how many leap seconds occurred during that interval. Therefore, many scientific applications that require precise measurement of long (multi-year) intervals use TAI instead  SONY VAIO VGN-FW51MF Battery .

TAI is also commonly used by systems which cannot handle leap seconds. A fixed 19-second offset from TAI also gives GPS time.

For most common and legal-trade purposes, the fractional second difference between UTC and UT (GMT) is inconsequentially small, so UTC is often called GMT (for instance, by the BBC)  SONY VAIO VGN-FW51MF/H Battery .

Time zones

Time zones usually differ from UTC by an integral number of hours, although the laws of each jurisdiction would have to be consulted if sub-second accuracy was required. Several jurisdictions established time zones that differ by an integer number of half-hours or quarter-hours from UT1 or UTC   SONY VAIO VGN-FW51ZF Battery .

The UTC time zone is sometimes denoted by the letter Z—a reference to the equivalent nautical time zone (GMT), which has been denoted by a Z since about 1950. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see time zone history)   SONY VAIO VGN-FW51ZF/H Battery .

Since the NATO phonetic alphabet and amateur radio word for Z is "Zulu", UTC is sometimes known as Zulu time. This is especially true in aviation, where Zulu is the universal standard. This ensures all pilots regardless of location are using the same 24-hour clock, thus avoiding confusion when flying between time zones   SONY VAIO VGN-FW52JB Battery .

See list of military time zones for letters used in addition to Z in qualifying time zones other than Greenwich.

On electronic devices that only allow the current time zone to be configured using maps or city names, UTC can be selected indirectly by selecting Reykjavik, Iceland, which is always on UTC time and does not use daylight saving   SONY VAIO VGN-FW54FB Battery .

Daylight saving

UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time or summer time. For example, UTC is 5 hours ahead of local time on the east coast of the United States during winter, but 4 hours ahead during summer  SONY VAIO VGN-FW70DB Battery .


The local mean solar time at the Royal Observatory, Greenwich, England, Great Britain, United Kingdom, was chosen at the 1884 International Meridian Conference to define the Universal day, counted from zero hours at mean midnight, in recognition of the widespread use of Greenwich Mean Time (GMT)   SONY VAIO VGN-FW71DB/W Battery .

In 1884, the Greenwich Meridian was used for two-thirds of all charts and maps as their Prime Meridian. In 1928, the term Universal Time (UT) was introduced by the International Astronomical Union to refer to GMT with the day starting at midnight. Until the 1950s, broadcast time signals were based on UT, and hence on the rotation of the Earth  SONY VAIO VGN-FW72JGB Battery .

In 1955, the caesium atomic clock was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1956, the U.S. National Bureau of Standards started to use atomic frequency standards in generating the WWV time signals, named for the shortwave radio station which broadcasts them  SONY VAIO VGN-FW73JGB Battery .

In a controversial decision, the frequency of the signals was initially set to match the rate of UT, but then kept at the same frequency by the use of atomic clocks and deliberately allowed to drift away from UT. When the divergence grew significantly, the signal was phase shifted (stepped) by 20 ms to bring it back into agreement with UT   SONY VAIO VGN-FW74FB Battery .

Twenty-nine such steps were used before 1960.The signal frequency was changed less often.

In 1958, the International Atomic Time (TAI) service started. It was based on the frequency for the caesium transition, newly established   SONY VAIO VGN-FW81HS Battery ,

that was later used to redefine the second in 1967, at a length practically equal to the second of ephemeris time. The WWV time signal's frequency was offset from the TAI frequency, so that clocks which followed the WWV signal would tick exactly one second for every 1.00000001 s ticked by clocks which followed the TAI signal   SONY VAIO VGN-FW81NS Battery .

Despite the initial controversy, it became clear that basing time signals on atomic clocks was an improvement over the prior system. However, it was widely desired to keep civil time synchronised with the Earth's rotation, and many uses of time signals (such as for navigation) relied on their closely matching Universal Time   SONY VAIO VGN-FW81S Battery .

WWV's compromise approach was copied by other agencies worldwide, such as the Royal Greenwich Observatory. It then became a concern that time signals should be synchronised with each other, rather than independently determining their own frequency offsets and phase shifts   SONY VAIO VGN-FW82DS Battery .

In 1960, an international agreement was made on atomic-based time signals. A frequency offset of 1.5 × 10?8 was adopted by all the participating institutions, matching the then-current rate of UT2, a version of UT1 smoothed from seasonal variations. Ad hoc phase shifts were used to synchronise the time signals as far as possible   SONY VAIO VGN-FW82JS Battery .

It was determined that the Bureau International de l'Heure should henceforth choose the frequency offsets and coordinate the time steps. It was also decided to use larger jumps, of 50 ms instead of 20 ms.

UTC was officially initiated at the start of 1961 (but the name Coordinated Universal Time was not adopted by the International Astronomical Union until 1967)    SONY VAIO VGN-FW82XS Battery .

The TAI instant 1 January 1961 00:00:01.422818 exactly was identified as UTC instant 1 January 1961 00:00:00.000000 exactly, and UTC ticked exactly one second for every 1.000000015 s of TAI. Time steps occurred every few months thereafter, and frequency changes at the end of each year   SONY VAIO VGN-FW83DS Battery .

The jumps increased in size to 100 ms, with only one 50 ms jump having ever occurred. This UTC was intended to permit a very close approximation of UT2, within around 0.1 s.

In 1967, the SI second was redefined in terms of the frequency supplied by a caesium atomic clock   SONY VAIO VGN-FW83JS Battery .

The length of second so defined was practically equal to the second of ephemeris time.This was the frequency that had been provisionally used in TAI since 1958. It was soon recognised that having two types of second with different lengths, namely the UTC second and the SI second used in TAI, was a bad idea   SONY VAIO VGN-FW83XS Battery .

It was thought that it would be better for time signals to maintain a consistent frequency, and that that frequency should match the SI second. Thus it would be necessary to rely on time steps alone to maintain the approximation of UT. This was tried experimentally in a service known as "Stepped Atomic Time" (SAT)    SONY VAIO VGN-FW90NS Battery ,

which ticked at the same rate as TAI and used jumps of 200 ms to stay synchronised with UT2.

There was also dissatisfaction with the frequent jumps in UTC (and SAT). In 1968, Louis Essen, the inventor of the caesium atomic clock, and G. M. R. Winkler both independently proposed that steps should be of 1 s only  SONY VAIO VGN-FW37J/B Battery.

This system was eventually approved, along with the idea of maintaining the UTC second equal to the TAI second. At the end of 1971, there was a final irregular jump of exactly 0.107758 TAI seconds, so that 1 January 1972 00:00:00 UTC was 1 January 1972 00:00:10 TAI exactly, making the difference between UTC and TAI an integer number of seconds  SONY VAIO VGN-FW37J Battery .

At the same time, the tick rate of UTC was changed to exactly match TAI. UTC also started to track UT1 rather than UT2. Some time signals started to broadcast the DUT1 correction (UT1 ? UTC) for applications requiring a closer approximation of UT1 than UTC now provided   SONY VAIO VGN-FW378J/B Battery .

The first leap second occurred on 30 June 1972. Since then, leap seconds have occurred on average about once every 19 months, always on 30 June or 31 December. As of 1 January 2010, 00:00:00 UTC, there have been 24 leap seconds in total, all positive, putting UTC 34 seconds behind TAI (this is the case since 1 January 2009)   SONY VAIO VGN-FW378DH Battery .

It seems unlikely that a negative leap second will ever occur, but there is a small chance of one due to changes in the moment of inertia of the Earth's crust in the 2000s.  This acceleration has already led to the longest-ever period without a leap second, from 1 January 1999 to 31 December 2005    SONY VAIO VGN-FW378J/B Battery .


The Earth's rotational speed is very slowly decreasing due to tidal deceleration, causing the mean solar day to increase in length. The length of the SI second was calibrated on the basis of the second of ephemeris time and can now be seen to have a relationship with the mean solar day observed between 1750 and 1892, analysed by Simon Newcomb   SONY VAIO VGN-FW37J Battery .

As a result, the SI second is close to 1/86400 of a mean solar day in around 1820. In earlier centuries the mean solar day was shorter than 86400 SI seconds, and in later centuries it is longer than 86400 seconds. At the end of the 20th century the length of the mean solar day (also known simply as "length of day" or "LOD") was approximately 86,400.002 s   SONY VAIO VGN-FW41E/H Battery .

For this reason, UT is now "slower" than TAI.

The excess of the LOD over the nominal 86,400 s accumulates over time, causing the UTC day, initially synchronised with the mean sun, to become desynchronised and run ahead of it    SONY VAIO VGN-FW41J/H Battery .

At the end of the 20th century, with the LOD at 2 ms above the nominal value, UTC ran faster than UT by 2 ms per day, getting a second ahead roughly every 500 days. Thus, leap seconds were inserted at approximately this interval, retarding UTC to keep it synchronised in the long term   SONY VAIO VGN-FW41M/H Battery .

Note that the actual rotational period varies on unpredictable factors such as tectonic motion and has to be observed, rather than computed.

The insertion of a leap second every 500 days does not indicate that the mean solar day is getting longer by a second every 500 daysSONY VAIO VGN-FWZJ/H Battery

(just as a leap day every four years does not mean the year is getting longer by one day every four years): it will take approximately 50,000 years for a mean solar day to lengthen by one second (at a rate of 2 ms/cy). This is a mean rate within the range of 1.7–2.3 ms/cy   Dell Inspiron 6400 AC Adapter .

The rate due to tidal friction alone is about 2.3 ms/cy, but the uplift of Canada and Scandinavia by several metres since the last Ice Age has temporarily reduced this to 1.7 ms/cy over the last 2700 years. The correct reason for leap seconds is not the current difference between actual and nominal LOD      Dell LATITUDE D800 battery ,

but rather the accumulation of this difference over a period of time: in the late twentieth century, this difference was about 1/500 of a second per day, so it accumulated to 1 second after about 500 days.

For example, assume you start counting the seconds from the Unix epoch of 1970-01-01T00:00:00 UTC with an atomic clock  Dell Inspiron Mini 12 battery .

At midnight on that day (as measured on UTC), your counter registers 0 s. After Earth has made one full rotation with respect to the mean Sun, your counter will register approximately 86400.002 s (the precise value will vary depending on plate tectonic conditions)   Dell Inspiron 1720 battery .

Based on your counter, you can calculate that the date is 1970-01-02T00:00:00 UT1. After 500 rotations, your counter will register 43,200,001 s. Since 86,400 s × 500 is 43,200,000 s, you will calculate that the date is 1971-05-16T00:00:01 UTC, while it is only 1971-05-16T00:00:00 UT1   Dell Inspiron 1564 battery .

If you had added a leap second on December 31, 1970, retarding your counter by 1 s, then the counter would have a value of 43,200,000 s at 1971-05-16T00:00:00 UT1, and allow you to calculate the correct date.

In the graph of DUT1 above, the excess of LOD above the nominal 86,400 s corresponds to the downward slope of the graph between vertical segments   Dell Inspiron 1764 battery .

(Note that the slope became shallower in the 2000s, due to a slight acceleration of the Earth's crust temporarily shortening the day.) Vertical position on the graph corresponds to the accumulation of this difference over time, and the vertical segments correspond to leap seconds introduced to match this accumulated difference   Dell Inspiron 1464 battery .

Leap seconds are timed to keep DUT1 within the vertical range depicted by this graph. The frequency of leap seconds therefore corresponds to the slope of the diagonal graph segments, and thus to the excess LOD.


As the Earth's rotation continues to slow, positive leap seconds will be required more frequently   Dell XPS 1340 battery .

The long-term rate of change of LOD is approximately +1.7 ms per century. At the end of the 21st century LOD will be roughly 86,400.004 s, requiring leap seconds every 250 days. Over several centuries, the frequency of leap seconds will become problematic   Dell INSPIRON 9100 battery .

Some time in the 22nd century, two leap seconds will be required every year. The current use of only the leap second opportunities in June and December will be insufficient, and the March and September options will have to be used. In the 25th century, four leap seconds will be required every year, so the current quarterly options will be insufficient    Dell Inspiron N4010 battery      .

Thereafter there will need to be the possibility of leap seconds at the end of any month. In about two thousand years even that will become insufficient, and there will have to be leap seconds that are not at the end of a month.

In a few tens of thousands of years (the timing is uncertain) LOD will exceed 86,401 s   Dell N3010 battery ,

causing the current form of UTC to break down due to requiring more than one leap second per day. It would be possible to then continue with double leaps, but this becomes increasingly untenable.

Both the one-leap-second-per-month and one-leap-second-per-day milestones are considered   Dell D6400 battery ,

to mark the theoretical limit of the applicability of UTC. The actual number of leap seconds to keep track of time would become unwieldy by current standards well before these, but presumably if UTC were to continue then horological systems would be redesigned to cope with regular leap seconds much better than current systems do   HP Pavilion DV6-1210SA battery .

There is a proposal to redefine UTC and abolish leap seconds, such that sundials would slowly get further out of sync with civil time. The resulting gradual shift of the sun's movements relative to civil time is analogous to the shift of seasons relative to the yearly calendar that results from the calendar year not precisely matching the tropical year length   HP Pavilion DM4 battery .

This would be a major practical change in civil timekeeping, but would take effect slowly over several centuries. An ITU study group was to have voted on this possibility during 2008, possibly leading to official approval by the World Radiocommunication Conference in 2012 and the subsequent cessation of leap seconds  HP Pavilion DM3 battery .

There is also a proposal that the present form of UTC could be improved to track UT1 more closely, by allowing greater freedom in scheduling leap seconds.

Sony Vaio VGN-CR23/W Battery .

The designers of Verilog wanted a language with syntax similar to the C programming language, which was already widely used in engineering software development. Verilog is case-sensitive, has a basic preprocessor (though less sophisticated than that of ANSI C/C++), and equivalent control flow keywords (if/else, for, while, case, etc.), and compatible operator precedence Sony Vaio VGN-CR23/N Battery .

Syntactic differences include variable declaration (Verilog requires bit-widths on net/reg types , demarcation of procedural blocks (begin/end instead of curly braces {}), and many other minor differences.

A Verilog design consists of a hierarchy of modules   Sony Vaio VGN-CR23/L Battery .

Modules encapsulate design hierarchy, and communicate with other modules through a set of declared input, output, and bidirectional ports. Internally, a module can contain any combination of the following: net/variable declarations (wire, reg, integer, etc.), concurrent and sequential statement blocks, and instances of other modules (sub-hierarchies)  Sony Vaio VGN-CR23/R Battery.

Sequential statements are placed inside a begin/end block and executed in sequential order within the block. But the blocks themselves are executed concurrently, qualifying Verilog as adataflow language.

Verilog's concept of 'wire' consists of both signal values (4-state: "1, 0, floating, undefined")  Sony Vaio VGN-CR23/P Battery ,

and strengths (strong, weak, etc.) This system allows abstract modeling of shared signal-lines, where multiple sources drive a common net. When a wire has multiple drivers, the wire's (readable) value is resolved by a function of the source drivers and their strengths  Sony Vaio VGN-CR23/B Battery .

A subset of statements in the Verilog language are synthesizable. Verilog modules that conform to a synthesizable coding-style, known as RTL (register transfer level), can be physically realized by synthesis software. Synthesis-software algorithmically transforms the (abstract) Verilog source into a netlist  Sony Vaio VGN-CR220E/R Battery ,

a logically-equivalent description consisting only of elementary logic primitives (AND, OR, NOT, flipflops, etc.) that are available in a specific FPGA or VLSI technology. Further manipulations to the netlist ultimately lead to a circuit fabrication blueprint (such as a photo mask set for an ASIC, or a bitstream file for an FPGA)  Sony Vaio VGN-CR21Z/R Battery .


Verilog was invented by Phil Moorby and Prabhu Goel during the winter of 1983/1984 at Automated Integrated Design Systems (renamed to Gateway Design Automation in 1985) as a hardware modeling language   Sony Vaio VGN-CR21Z/N Battery .

Gateway Design Automation was purchased by Cadence Design Systems in 1990. Cadence now has full proprietary rights to Gateway's Verilog and the Verilog-XL simulator logic simulators. Originally, Verilog was intended to describe and allow simulation; only afterwards was support for synthesis added  Sony Vaio VGN-CR21S/W Battery .


With the increasing success of VHDL at the time, Cadence decided to make the language available for open standardization. Cadence transferred Verilog into the public domain under the Open Verilog International (OVI) (now known as Accellera) organization  Sony Vaio VGN-CR21S/P Battery .

Verilog was later submitted to IEEE and became IEEE Standard 1364-1995, commonly referred to as Verilog-95.

In the same time frame Cadence initiated the creation of Verilog-A to put standards support behind its analog simulator Spectre. Verilog-A was never intended to be a standalone language and is a subset of Verilog-AMS which encompassed Verilog-95 Sony Vaio VGN-CR21S/L Battery .

Verilog 2001

Extensions to Verilog-95 were submitted back to IEEE to cover the deficiencies that users had found in the original Verilog standard. These extensions became IEEE Standard 1364-2001 known as Verilog-2001  Sony Vaio VGN-CR21E/W Battery .

Verilog-2001 is a significant upgrade from Verilog-95. First, it adds explicit support for (2's complement) signed nets and variables. Previously, code authors had to perform signed-operations using awkward bit-level manipulations (for example, the carry-out bit of a simple 8-bit addition required an explicit description of the boolean-algebra to determine its correct value) Sony Vaio VGN-CR21E/P Battery .

The same function under Verilog-2001 can be more succinctly described by one of the built-in operators: +, -, /, *, >>>. A generate/endgenerate construct (similar to VHDL's generate/endgenerate) allows Verilog-2001 to control instance and statement instantiation through normal decision-operators (case/if/else)   Sony Vaio VGN-CR21E/L Battery .

Using generate/endgenerate, Verilog-2001 can instantiate an array of instances, with control over the connectivity of the individual instances. File I/O has been improved by several new system-tasks. And finally, a few syntax additions were introduced to improve code-readability Sony Vaio VGN-CR21/B Battery .

Verilog-2001 is the dominant flavor of Verilog supported by the majority of commercial EDA software packages.

Verilog 2005

Not to be confused with SystemVerilog, Verilog 2005 (IEEE Standard 1364-2005) consists of minor corrections, spec clarifications, and a few new language features (such as the uwire keyword)  Sony Vaio VGN-CR190E/W Battery .

A separate part of the Verilog standard, Verilog-AMS, attempts to integrate analog and mixed signal modeling with traditional Verilog.


SystemVerilog is a superset of Verilog-2005, with many new features and capabilities to aid design-verification and design-modelingSony Vaio VGN-CR190E/R Battery .

As of 2009, the SystemVerilog and Verilog language standards were merged into SystemVerilog 2009 (IEEE Standard 1800-2009).

The advent of hardware verification languages such as OpenVera, and Verisity's e language encouraged the development of Superlog by Co-Design Automation Inc  Sony Vaio VGN-CR190E/P Battery .

Co-Design Automation Inc was later purchased by Synopsys. The foundations of Superlog and Vera were donated to Accellera, which later became the IEEE standard P1800-2005: SystemVerilog  Sony Vaio VGN-CR190E/L Battery .

Partager cet article

Repost 0
Published by batterys - dans Laptop Battery
commenter cet article