echo cancellation


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echo cancellation

A process which removes unwanted echoes from the signal on a telephone line. Echoes are usually caused by impedance mismatches along an analogue line.

echo cancellation

The elimination of an echo in a two-way voice transmission. Echo is created in the telephone company's central office switch when two-wire lines from the customer are converted to four-wire lines for backbone trunks. The echo is exacerbated over longer distances and by certain kinds of network equipment. A delay of 30ms or more is noticeable, and 50ms is annoying. To eliminate it, the carriers put echo cancellers on their switch ports and in their long-distance trunks at 500 mile intervals.

Using sophisticated DSP circuits that isolate the echo and transmit a reverse frequency to cancel it, echo cancellation is also built into analog modems, speakerphones and quality sound cards. See echo suppression and noise cancellation.
References in periodicals archive ?
SoftEcho handles double-talk and background noise better than the generic echo cancellation solutions currently integrated into popular Asterisk PBX systems.
Network designers can easily place this echo canceler chip at the location closest to where the echo is generated, providing superior echo cancellation performance.
The chip, which implements codec and 64-tap echo cancellation functions for four telephone lines, provides programmable control of key performance parameters, including gain, hybrid balance, termination impedance, equalization, and echo cancellation.
Octasic Semiconductor's internationally deployed carrier-grade echo cancellation solutions, delivering unprecedented voice quality.
LSI said that its ECAN software provides a robust set of real-world VoIP communications features including a maximum tail length of 128ms, the ability to detect and compensate for up to three windows with the tail, rapid convergence, and 24ms of active echo cancellation.
Since the ability to provide voice quality of the highest standard depends mainly on selecting the right echo cancellation technology, Adaptive Digital's highly regarded "carrier-class" G.
McConnell goes on to say that DS1 echo cancelers can be set up to turn off the cancellation on certain channels, but this solution falls apart when the number of data devices that need the echo cancellation turned off exceeds the number of channels that have cancellation off.
Engage has responded to the increased demand for transporting TDM based voice traffic over IP and Ethernet networks by doubling the Echo Cancellation capacity in the same compact footprint, The new 4 port IP-Tube G with Echo Cancellation is based on Engage Communication proven technology and has already been delivered to a major international MSO for backhauling their business customer's PBX E1 circuits over their hybrid cable infrastructure.
By scaling down its echo cancellation solution to 32 and 64 channels, Octasic can look towards capitalizing on the tremendous growth opportunity in the enterprise IP-PBX market", said Ronald Gruia, Program Leader, Enterprise Communications Solutions at Frost and Sullivan.
New Card Supports Digium's Hardware Echo Cancellation Module to Provide Unrivaled Echo Cancellation for Multi-Port Open Source VoIP Systems
7 /PRNewswire/ -- A complete DSP-based echo cancellation solution based upon TI's TMS320C5441 device and Telinnovation echo cancellation software is now available from Texas Instruments Incorporated (TI), a result of TI's acquisition of Ditech's Telinnovation Echo Cancellation Software Unit in April 2002.