Patent ID: 7142665

Claim:
An echo cancellation system comprising: an automatic gain control unit for receiving a first signal and a second signal, said automatic gain control unit responsive to said second signal having an automatic gain control algorithm, wherein said automatic gain control algorithm has a time constant in a range of 1–10 milliseconds; a first scalar coupled to receive said second signal and providing a scaled second signal, said first scalar being responsive to said automatic gain control; a signal summing stage coupled said first scalar for receiving said scaled second signal and a third signal, said signal summing stage providing a fourth signal having an echo signal removed therefrom; a second scalar coupled to said summing stage for receiving said fourth signal and providing a scaled fourth signal, said second scalar being responsive to said automatic gain control wherein a scaling rate of said second scalar is an inverse of a scaling rate of said first scalar; and an adaptive filter for receiving said first signal and generating said third signal that corresponds to said echo signal, said adaptive filter having said maximum coefficient.