| 摘要 |
PURPOSE:To always attain effective cancellation of echo, by detecting the change in an echo path characteristic and suitably setting the timing of training. CONSTITUTION:A training signal from a training signal generating circuit 7 is applied to a hybrid circuit 1, in place of a transmission signal applied via a transmission amplifier 4 from a switch circuit 6 controlled with a line fluctuation detector 8. A virtual echo signal generator 2 estimates the echo path characteristics based on the training signal and holds the estimated value. Further, the swtich circuit 6 is changed over, a transmission signal is applied to the hybrid circuit 1 for communication. If line fluctuation takes place during the communication, the line fluctuation detector 8 detects this fluctuation, the switch circuit 6 is changed over, and the virtual echo signal generator 2 is controlled to the estimation mode. Thus, the virtual echo signal generator 2 again makes estimation. |
