The 48-channel transcoder provides for the conversion between two 24-channel 1544 kbit/s PCM streams and one 48-channel 1544 kbit/s ADPCM stream. In the 24-channel 1544 kbit/s streams, the voice-frequency signals are coded at 64 kbit/s according to the PCM µ-law defined in Recommendation G.711. In the 48-channel 1544 kbit/s stream, the voicefrequency signals are coded at 32 kbit/s according to the ADPCM encoding law defined in Recommendation G.721.