PURPOSE: To eliminate effectively an echo signal despite the interruption of a conversation or the circuit switching, by monitoring a remaining echo signal and clearing an estimated impulse answer series based on the scale of the remaining echo signal to start a converging operation.
CONSTITUTION: An echo route includes a hybrid circuit, etc. and is connected to a subscriber via a switch board (not shown in the diagram). A deciding circuit 14 of a monitor circuit 7 delivers a clear signal 15 to an estimated impulse answer storage circuit 5. A received signal and the output signal of the circuit 5 are applied to a convolutional integration circuit 3, and a pseudo echo signal is produced. This pseudo echo signal is substrated from a transmitted signal to eliminate the echo signal. The circuit 5 clears the impulse answer series only when the signal 15 arrives and then starts a converging operation. Therefore, the answer series is held when a conversation is interrupted. When the received signal arrives, an eliminating mode set before the interruption is reset. The signal 15 is delivered if the frequency of the remaining echo signal is high when the received signal arrives. Then the estimated impulse answer series is cleared, and a converging operation is started.
KOSHIKAWA MASAMI
TANIGUCHI TOMOHIKO
| JPS5789337A | 1982-06-03 |
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