A 60 Channel PCM-ADPCM Converter

Coding techniques based on adaptive linear prediction and quantization are well suited to signals carried by telephone channels and can provide, with a per channel rate of 32 kbits/s, a level of quality compatible with the specifications of the conventional 64 kbit/s rate. The ADPCM technique described in this paper features a simple adaptive quantization scheme and a tenth-order linear prediction adaptive filter realized as a cascade of five second-order sections. Besides superior performance characteristics, the nonaccumulation of degradations in tandem connections is achieved. The implementation is a 60 channel PCM-ADPCM converter, called TMN 162. It is a fully digital equipment which offers a doubling of the capacity of digital links in telephone networks.