| 摘要 |
PURPOSE:To estimate effectively an echo path characteristic,by transmitting a training signal before the start of service. CONSTITUTION:When an output is issued from one of an originating discriminator 9 to be called, a receiving detector 10, and a call detector 11, a control circuit regulates the timing for supply of a training signal and the timing for estimation of an echo path characteristic and supplies the output of a training signal generator 6 to an echo canceler circuit 7 and a hybrid circuit 3. The echo cancler circuit 7 estimates the echo path characteristic on a basis of the training signal and the echo signal from the hybrid circuit 3. Next, the control circuit closes a switch 1 and switches a changeover switch 5 to the amplifier 2 side. Thus, the echo canceler circuit 7 generates a false echo signal and the false signal is subtracted from the receiving signal from the hybrid circuit 3 at the service time, thereby eliminating the echo. |
