The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the Intemational TelecommunicationUnion (ITU).CCITT is responsible for studying technical,operating and tariff questions and issuing Recommendationson 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 CCITT between Plenary Assembliesis covered by the procedure laid down in CCITI’Resolution No.2 (Melbourne, 1988).Recommendation 1.253.2 was revised by Study Group I and was approved under the Resolution No. 2 procedureon the 4th of August 1992