PULSE TRANSMISSION SYSTEMS

In a differential pulse code modulation system, the integration of a pulse train representing a delta modulation coded format of an analog signal is modified by injection of at least one current of a magnitude corresponding to a predetermined fractional delta modulation step and of a polarity which indicates whether or not a delta modulation pulse was present in a predetermined phase of each recurring differential pulse code modulation accumulating period of the system. In a system coder, the initiation of the injected signal also causes the addition of a corresponding least significant bit to the accumulator output transmitted to a decoder. That least significant bit is utilized in the decoder to produce a corresponding current for injection into the equivalent integrating system of the decoder.