Comité Consultatif Internationale de Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee), originally, an agency of the International Telecommunications Union (ITU), itself an agency of the UN. The CCITT acted as a worldwide coordinating agency for telephone and data communications systems, dealing with regulatory matters and with technical standards. The voting members of the CCITT included the national telecommunications administrations such as the FCC and the PTTs in Europe, and recognized private administrations such as AT&T and BT. Nonvoting members included scientific and industrial organizations and standards bodies such as ISO.
The CCITT produced definitive versions of the standards to be used in both national and international telecommunications. CCITT standards are categorized by an initial letter, which indicates the broad topic area for the material, and a decimal number, which identifies the particular standard. Standards specifically relating to data transmission have the letter V (over analog circuits (see V) or X (over digital circuits (see X); standards relating to ISDN have the letter I while standards for monitoring and controlling communications systems have the letter M. Where there have been major revisions of standards that have been in use for some time, the number will be followed by either bis or ter, indicating a second or third version of the standard.
In 1992, there was a reorganization of the ITU, which led to the CCITT being renamed as the ITU-T (International Telecommunications Union — Telecommunication Standardization Sector; see ITU).