The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of
the International Telecommunication Union (ITU).CCITT is responsible for studying technical, operating and tariff
questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide
basis.
The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves
Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCI?iT
between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988).
Recommendation 1.251.4 was prepared by Study Group I and was approved under the Resolution No. 2
procedure on the 4th of August 1992.