A New PCM Exchange Carrier System

This paper describes a 24-channel pulse code modulation (PCM) cable carrier system designed for interexchange applications. The system is compatible with Western Electric T1 carrier. All digital functions are accomplished with only two types of integrated circuit elements, a dual 2-input gate and a JK flip-flop. Simple unbalanced transistor channel gates are used for speech sampling at the transmitting end and sample distribution at the receiving end. The single instantaneous compander uses temperature-controlled diodes. A resampling circuit eliminates the need for dual compressors and encoders at the transmitting end and also provides automatic centering of the compressor characteristic.