The International Telecommunications Union (ITU) is a specialized agency of the United Nations, headquartered in Geneva, Switzerland. The telecommunications section of the ITU(ITU -T) is tasked with direct responsibility for developed data communications standards and consists of 15 Study

Groups, each tasked with a specific area of responsibility. The work of the ITU-T is performed on a four-year cycle which is known as a Study Period. At the conclusion of each Study Period, a Plenary Session occurs.

During the Plenary Session, the work of the ITU-T during the previous four years is reviewed, proposed recommendations are considered for adoption and items to be investigated during the next four-year cycle are considered.

The ITU-T Tenth Plenary Session met in 1992 and its eleventh session occurred in 1996. Although approval of recommended standards is not intended to be mandatory, ITU-T recommendations have the effect of law in some Western European countries and many of its recommendations have been adopted by both communications carriers and vendors in the United States.

ITU-T recommendations
Recommendations promulgated by the ITU-T are designed to serve as a guide for technical, operating and tariff questions related to data and telecommunications. ITU-T recommendations are designated according to the letters of the alphabet, from Series A to Series Z, with technical standards included in Series G to Z.

In the field of data communications, the most well known ITU-T recommendations include Series I which pertains to Integrated Services Digital Network (ISDN) transmission, Series Q which describes ISDN switching and signaling systems, Series V which covers facilities and transmission systems used for data transmission over the PSTN and leased telephone circuits, the DTE-DCE interface and modem operations and Series X which covers data communications networks to include Open Systems Interconnection (OSI).

One emerging series of ITU-T recommendations that can be expected to become relatively well known in the next few years is the G.922 recommendations. The G.922 recommendations define standards for different types of digital subscriber lines to include splitterless G.lite.

The ITU-T V-Series
For international use, the V.3 recommendation specifies national currency symbols in place of the dollar sign ($) as well as a few other minor differences. You should also note that certain ITU-T recommendations, such as V.21, V.22 and V.23, among others, while similar to AT&T Bell modems, may or may not provide operational compatibility with modems manufactured to Bell specifications.

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