| 摘要 |
PURPOSE:To make the insertion loss proper, to make a sevice without the impresstion of swtching prossible, and to prevent howling effectively, by using effectively merits of the echo canceller system and the voice switch. CONSTITUTION:A switch circuit 15 receives the control of a control circuit 17 to supply a training signal from a training signal generator 16 to a hybrid 3, and an echo canceller circuit 18 estimates an echo path (side tone characteristics) of the hybrid 3 on a basis of the training signal and the side tone from the hybrid 3, and a loss determining circuit 14 determines loss quantities of variable loss circuits 11 and 12 on a basis of the side tone level. The echo canceller circuit subtracts a false side tone from the receiving signal, and a comparing circut 13 compares the output level of an amplifier 5 and the output level of the echo can celler 18 with each other to insert the loss quantity to the transmissin line at the receiving time and insert it to the receiving line at the transmission time. |
