| 摘要 |
The proposed echo canceller comprises:
- an adaptive filter for receiving a signal affected by an echo, and for supplying a filtered signal that is an estimate of the echo;
- a subtractor for subtracting this estimate from the received signal and supplying a residual signal;
- means for detecting (7, 8) a ring back tone in said residual signal;
- means for blocking (9) the received signal and replacing it by a locally generated ring back tone if a ring back tone is detected in the received signal;
- a timer to determine a time period;
- and means (11-17) for, during said time period, replacing the residual signal by some synthetic comfort noise when there is no ring back tone. |
