| 摘要 |
A loudspeaking telephone with a variable gain circuit comprises a receiving path including first amplifying means for amplifying a received signal by a first gain to provide a received speech signal. A transmitting path includes second amplifying means for amplifying a transmitted speech signal by a second gain to provide a transmitted signal and first means for comparing a signal level on the receiving path with a signal level on the transmitting path to provide a control signal to control the first and the second gains. Second means responsive to the control signal for switching between the first and second gains are provided to make one of the gains larger than the other of the gains wherein the total gain obtained from the first and second gains during the changeover period of the gains is either equal to or smaller than the total gain during the stable period excluding the changeover period. |
