| 摘要 |
An echo canceller for a long-distance telephone circuit comprising a hybrid whereby a branch network supplied by the signals of the incoming direction of the four-wire path is provided with a number of outputs which correspond to systems having pulse responses which are linearly independent from each other provides output signals which are directed by way of gain elements to an adder whose output signal is subtracted as a simulated echo signal from the signals of the outgoing direction of the four-wire path. Each gain element can be adjusted by the integrated output signal of a multiplying arrangement which multiplies the respective output signal of the branch network with the remaining echo signal which is being weighted with one or several weighting factors in the outgoing direction of the four-wire path. A control arrangement is fed by the output signals of the branch network and the remaining echo signal, the control arrangement controlling the weighting factor or factors in such a way that the weighting factors normally accept the maximum value and are attenuated in case of the occurrence of interfering noise in the outgoing direction of the four-wire path greater the stronger the interfering noise and the better the already achieved setting accuracy of the gain elements, such as for example in the case of the occurrence of speech signals of the near-end subscriber. |
