Use of a digital echo canceler in the AT&T Domsat intertoll network

The 4A echo canceller in the AT&T Domsat intertoll network provides up to 28 dB of echo return loss enhancement, uses a center clipper to eliminate residual echo, and meets CCITT Recommendation G.164. This canceller improved the voice quality of full-hop satellite circuits by reducing the amount of talker echo when compared to satellite circuits with echo suppressors. The center clipper is an important feature, and attention to insuring at least 6 dB of echo return loss in the network is necessary.