Echo Suppressor Design in Telephone Communications
Paul T. Brady, George K. Helder · Bell System Technical Journal · 1963
An elementary echo suppressor is described which consists of a single voice-operated switch located at each end of a four-wire toll connection. It is shown that this circuit is unsuitable for telephone conversations if there is an appreciable delay between the speakers. Modifications and additions to the elementary echo suppressor are made in an effort to improve its performance. Action in the presence of break-in speech is discussed in some detail. The operation of four present-day echo suppressors is described