| 摘要 |
PCT No. PCT/GB82/00329 Sec. 371 Date Jul. 15, 1983 Sec. 102(e) Date Jul. 15, 1983 PCT Filed Nov. 18, 1982 PCT Pub. No. WO83/01876 PCT Pub. Date May 26, 1983.There is disclosed a communications system in which digital information is conveyed over a line and each station on the line has a hybrid circuit. The invention includes an apparatus having means for cancelling an unwanted echo signal between receive and transmit channels at each station. An analog to digital converter in the receive channel has a control input to receive a timing signal. A subtractor circuit has a first input coupled to the output of the digital to analog converter through a filter and receives signals from a canceller sample and hold circuit having an input coupled to the transmission port. The adaptive echo simulator is a transversal filter which has varying coefficient capability and which coefficients are varied by means of multiplexers included in coefficient generators. Thus the coefficient generators will provide coefficient outputs at given delays to enable the echo cancelling function to track the sytem response to produce a continuous signal whereby the unwanted signal is substantially removed as compared to operation of typical prior art echo cancellers. |
