Abstract: An echo canceller in a telephone circuit for minimizing a residual echo obtained by subtracting a pseudo-echo reproduced from an impulse response of an echo path from a true echo, in which the inpulse response is corrected by the use of the product of the residual echo and received input. A variable coefficient circuit is provided between a multiplier for obtaining the product and a circuit for correcting the impulse response. A control circuit is provided for reducing the coefficient of the variable coefficient circuit in accordance with the lapse of time of the duration of the received input exceeding a predetermined threshold level after receiving a circuit connection completion signal of the telephone circuit.

Abstract: An echo cancelling system for multiplex circuits, in which an impulse response of an echo-path is obtained from signals at respective ends of the transmission path and the receiving path connected to the echo-path to produce an echo-path model, and in which a pseudo echo signal is then provided to subtract it from an echo signal of the echo-path thereby to cancel the echo signal.