pulse code modulation (PCM) multiplex equipments are already used in various countries, in particular to provide a large number of short-distance telephone circuits on certain pairs in existing cables, and in order to minimize the number of different PCM multiplex equipments providing circuits which may be used in international connections,
ITU-T G.731-1993 Referenced Document
ITU-T G.731 PRIMARY PCM MULTIPLEX EQUIPMENT FOR VOICE FREQUENCIES
ITU-T G.732 CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT OPERATING AT 2048 kbit/s
ITU-T G.731-1993 history
1993ITU-T G.731-1993 PRIMARY PCM MULTIPLEX EQUIPMENT FOR VOICE FREQUENCIES