60 MHz FREQUENCY-DIVISION MULTIPLEX NETWORK.

The increasing traffic requirements of the late-1960s indicated a need to extend the circuit capacity of coaxial cables on which major telecommunication undertakings were operating 12 MHz frequency-division multiplex (FDM) systems on trunk routes. Feasibility studies initiated by the CCITT indicated that, by taking advantage of semiconductor technology, standard 2. 6/9. 5 mm coaxial cable could be exploited up to 60 MHz (nominal), with repeaters spaced at 1. 5 km intervals. The provision of the 60 MHz frequency-division network, which is now approaching completion.