Installation guide

Adjusting IP call quality parameters 6-41
Chapter 6: IP Telephony Configuration
Wave Global Administrator Guide
Echo cancellation
Caution: This is an expert setting that should not be modified unless you are instructed
to do so by your Vertical Technical Support representative.
Echo in a phone network is caused by signal reflections generated by the hybrid circuit that
converts between a 4-wire circuit (a separate transmit and receive pair) and a 2-wire circuit (a
single transmit and receive pair). Echo is present even in a conventional circuit switched phone
network. However, it is acceptable because the round trip delays through the network are
smaller than 5 ms and the echo is masked by the normal side tone every phone generates.
Perceived echo becomes a problem in packet-switched networks because the round trip delay
through the network is almost always greater than 5 ms. Thus, echo cancellation techniques are
often used.
Echo is generated toward the packet-switched network from the TDM phone network. The echo
canceller compares the voice data received from the packet-switched network with voice data
being transmitted to the packet-switched network. The echo from the phone network hybrid is
removed by a digital filter on the transmit path into the packet-switched network.
To adjust the echo cancellation settings
1 If necessary, click the Administration tab of the Management Console.
2 Click the IP Telephony icon, located in the PBX Administration section.
Click
Release 2.0
September 2010