The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to
ITU-T Q.709-1993 history
1993ITU-T Q.709-1993 Signalling System No. 7 - Hypothetical Signalling Reference Connection - Specifications of Signalling System No. 7 (Study Group XI) 17 pp