A conferencing technique for adaptive delta modulation

Abstract

A technique for digital conferencing of voice signals in systems using adaptive delta modulation (ADM) with an idle pattern of alternating 1's and 0's has been described. Based on majority logic, it permits distortion-free reception of voice of a single active subscriber by all the other subscribers in the conference. Distortion exists when more than one subscriber is active and the extent of this distortion depends upon the type of ADM algorithm that has been used. An LSI oriented system based on time sharing of a common circuit by a number of channels has been implemented and tested. This technique, with only minor changes in circuitry, handles ADM channels that have idle patterns different from alternating single 1's and 0's.