Echo-cancelling system comprising echo-cancelling devices connected in cascade, capable of operating independently of one another

摘要

In an echo-cancelling system replying to a transmission-input signal including an echo signal and to a reception-input signal, a plurality of local echo-cancelling devices are connected in series by way of an additional delay circuit between two contiguous cancelling devices in such a way as locally to cancel out portions of the echo signal. The reception-input signal x is successively delayed by a delay circuit 41 so as to be supplied to the cancelling devices 21-23 in the form of delayed signals which have different delays with respect to the reception-input signal and which correspond to the portions of the echo signal. Each cancelling device 21-23 produces a signal with the echo partially cancelled out by use of a transverse filter 26, 28, 33 and an adder 27, 29, 34. Each signal with the echo partially cancelled out is applied to the transverse filter of each cancelling device and to the additional delay circuit. The cancelling devices are operated independently of one another. IMAGE