Numbering in Systems on Symmetric Pair Cable - General Maintenance Principles - Maintenance of International Transmission Systems and Telephone Circuits (Study Group IV) 4 pp
In systems of the 12 + 12 type, 12 go and 12 return channels constitute one 12 circuit group.For the arrangement of the line frequencies transmitted for 12 + 12 cable systems using transistors, the Administrations concerned in setting up such an internati