The International Telecommunication Union (ITU) was founded on 17 May 1865 in Paris by 20 countries and has been a sub-organization of the United Nations(UN) with its headquarters in Geneva since 15 October 1947. As of August 1993, its membership numbered 181. The ITU is a worldwide organization in which governments and the private telecommunications sector coordinate the construction and operation of telecommunications networks and services.
The ITU has responsibility for the regulation, standardization, coordination and development of international telecommunications, and for the harmonization of national policy interests. The work was previously carried out in the 4 committees Telecommunications Development Bureau (BDT), Comité Consultatif International des Radiocommunications( CCIR), Comité Consultatif International Télégraphique et Téléphonique( CCITT) and International Frequency Registration Board( IFRB). After a structural reform of the ITU in December 1992, a new constitution came into force on July 1, 1994. The new ITU structure consists of 3 sectors (offices), each headed by a director: Radiocommunication (ITU-R), Telecommunication Standardization( ITU-T) and Telecommunication Development (ITU-D).
The previous CCITT Recommendations are superseded by the ITU Recommendations.
The ITU Recommendations use a letter-number combination for their identification, with the letter describing the scope.
A series: ITU internal organization, procedures, committees.
B-series: technical terms, definitions, symbols, abbreviations.
D-series: costs, tariffs.
G-series: wireline and wireless transmission technology.
H-series: use of lines for services other than telephony.
J series: Radio and television.
K-Series: Protection against external disturbances, such as interference.
L-Series: Mechanical protection of equipment.
N-series: Maintenance and quality of broadcasting systems.
P-series: telephone transmission quality, terminal characteristics.
Q-series: telephone signalling, telephone switching.
R-series: teletype equipment.
S series: terminals for telegraph services.
T series: terminals for telematics services.
U series: signalling in telegraph networks.
X series: data transmission networks; well-known standards such as X. 24, X. 21, X. 25, X. 400.
Z-series: documentation and programming languages.
The address is:
International Telecommunication Union, Place des Nation, CH-1211 Geneva 20, Switzerland.