An echo canceller circuit is set forth. The echo canceller circuit
includes a digital filter having adaptive tap coefficients to simulate an
echo response occurring during a call. The adaptive tap coefficients are
updated during the call using a Means Squares process. A tap energy
detector is also employed. The tap energy detector identifies and divides
groups of taps having high energy from groups of taps having low energy.
The high energy tap groups are smaller in number than the low energy tap
groups. The high energy tap groups are adapted separately from the low
energy tap groups using the Least Squares process. Still further, the
high energy tap groups may be adapted using an adaptive gain constant
.alpha. while the low energy tap groups are adapted using an adaptive
gain constant .alpha.', wherein .alpha.>.alpha.'.