Abstract This document describes the implementation of a coupled echo canceler (or named total echo canceler) on a 56K PCM modem. It gives an overview of the 56K PCM technology and the need of using a coupled echo canceler (EC) at the receiver of the client modem in order to alleviate the reception errors during high speed data transmissions. The author has provided theoretical analysis of both decoupled EC and coupled EC and shown that coupled EC decreases the residual echo in...