The 48-channel primary multiplexer provides conversion between 48 voice-frequency channels and one 1544 kbit/s ADPCM stream. In the 1544 kbit/s stream, the voice-frequency signals are coded according to the PCM encoding law defined in Recommendation G.711 and the ADPCM encoding law defined in Recommendation G.721. In addition, it may be arranged to provide limited 64 kbit/s unrestricted channel transfer capacity for baseband digital channel.
ITU-T G.724 SPANISH-1993 history
1993ITU-T G.724 SPANISH-1993 CHARACTERISTICS OF A 48-CHANNEL LOW BIT RATE ENCODING PRIMARY MULTIPLEX OPERATING AT 1544 kbit/s