Patent ID: 6901143

Claim:
A voice switching system comprising: a transmitting side attenuation section for attenuating a microphone input voice signal having a first level to produce a transmitted voice signal having a second level; a receiving side attenuation section for attenuating a received voice signal having a third level to produce a speaker output voice signal having a fourth level; a transmitting side control section for comparing said first level of said microphone input voice signal with said fourth level of said speaker output voice signal to obtain a first difference therebetween, said transmitting side control section controlling, dependent on said first difference, an amount of attenuation of said microphone input voice signal in said transmitting side attenuation section; and a receiving side control section distinct from the transmitting side control section and for comparing said second level of said transmitted voice of signal with said third level of said received voice signal to obtain a second difference therebetween, said receiving side control section controlling, dependent on said second difference, an amount of attenuation of said received voice signal in said receiving side attenuation means, the receiving side control section further comprising: a transmitting side signal delay buffer for providing said transmitted voice signal with a delay time, said delay time corresponding to a time for which said transmitted voice signal returns as said received voice signal through a communication line; a transmitting side signal power estimation section for estimating a signal power of said transmitted voice signal outputted from said transmitting side signal delay buffer; a receiving side signal power estimation section for estimating a signal power of said received voice signal; a comparator for comparing said estimated signal power of said transmitted voice signal estimated by said transmitting side signal power estimation section with said estimated signal power of said received voice signal estimated by said receiving side signal power estimation section to obtain a ratio therebetween; and a first attenuation amount calculation section for calculating an amount of attenuation in said receiving side attenuation section based on said ratio outputted from said first comparator.