A signal processing technique for multiplexed conversion of a large number of speech channels into adaptive delta modulation channels has been presented. This is based on fast decision circuits, buffer memories, and pipelined processing. A microprocessor control circuit permits channel switching through buffer memories, making it attractive for LSI oriented small exchanges.

A digital conferencing technique based on pseudo-addition of adaptive delta-modulated channels has been presented. It employs majority logic for routing speech signals of active subscriber to all others in conference. Time sharing allows processing of large number of channels, making it attractive for VLSI realization.

Design of a unit which handles functions of line scanning, digit forming, and digit pulsing fully independent of the main processor has been presented. These functions as implemented in conventional systems form a major portion of the real time load on the processor. The hardware unit described in this paper takes care of all these functions with only nominal interaction with the processsor, thereby reducing considerably the real time load. In this unit one very high speed logic assembly is shared by a large number of lines with the help of memory and timing circuits. The same hardware with only minor modifications can be used for telex application also. A typical unit for 1000 lines requires about 300 IC's. This includes the processor interface.