| 摘要 |
In an echo cancelling arrangement, an estimated echo signal is produced by an adaptive filter from a receive path signal and is subtracted from an incoming transmit path signal to produce an outgoing transmit path signal, to compensate for ERL (echo return loss) via a hybrid circuit. Short-term averages of signal levels on the receive path and the incoming and outgoing transmit paths are produced by exponential averaging. An ERLE (echo return loss enhancement) due to the subtraction of the estimated echo signal is calculated from the incoming and outgoing transmit path averages and, when this exceeds a threshold value, enables averaging of a ratio of average levels on the receive path to average levels on the incoming transmit path. The resulting long-term average constitutes a determination of the actual ERL.
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