A new design for program‐controlled voice switching circuits using a microprocessor

Abstract

The voice switching circuit (VS) is applied widely to various problems, including echo suppression and howling suppression in the communication equipment, realizing the magnified voice communication using microphones and loudspeakers. It is also applied frequently in recent years in combination with the echo canceller, in a form to complement the performance of the echo canceller.Kato et al. 131 discussed in detail the operational performance and the design method when VS is realized by the analog circuit, and proposed the automatic loss switchmg VS (ALS), where the switching loss is reduced by automatically adapting to the change of the acoustic and side-tone characteristics.In their method, however, A L S is constructed using 1 only the analog circuit. Ths makes the design complicated and makes it difficult to reduce the switching loss compared to the present design. With this in mind, the goal here is to realize the ALS function by program control, using the microprocessor (pP). The following two program-controlled VS with excellent voice communication functions are proposed:(1) VS applied to the whole speech band (type A);(2) the communication band is divided, and VS is applied tr> each of the divided subbands (type B).