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 ?
DALLAS, May 16 /PRNewswire/ -- Ratcheting voice quality one notch higher, Texas Instruments, Incorporated (TI) today has deployed its Telinnovation(TM) echo canceller software across several digital signal processor (DSP) platforms including the carrier infrastructure optimized TNETV3020, as well as TMS320C64x(TM)- and TMS320C64x+(TM) -based devices.
GL Communications has introduced its new and enhanced echo canceller testing tools, which were designed to enable communications carriers and equipment manufacturers to improve the voice quality of wireline and wireless networks.
While competitors require their customers to purchase individual daughter-boards costing several hundred dollars to provide voice enhancement capabilities, Ditech's VQoS software comes bundled as part of the standard Ditech echo canceller.
Expanded Product Line Includes New Telephony Interface Cards and High Performance Software Based Echo Canceller
There is much to be learned from the deployment of a network echo canceller in a wide variety of equipment over a span of many years.
ZL(TM)38002 acoustic echo canceller with enhanced noise reduction delivers superior sound quality for hands-free communications, including car kits, speakerphones, security and intercom systems
729AB, and a range of other codecs, Network Line Echo Canceller, various tones detection and generation, other telephony components, Fax and Data Modems, and a suite of software utilities simplifying the application development.
Octasic has set up two demonstration phone lines - one with Music Protection enabled on the echo canceller and the other without any Music Protection functionality.
With the advent of its eSound Engine, which Oki has been providing since March 2006, Oki succeeded to offer high quality and stable communications over IP networks by adding its original packet loss concealment (PLC) feature and wideband echo canceller to wideband codecs such as G.
Based upon TI's TMS320C55x(TM) DSP platform and Telinnovation echo cancellation software, the solution features significant enhancements to the echo canceller algorithm and a major increase in channel density over previous products.
For telecommunications carriers developing packet-based voice transmission systems, the Telinnovation high- capacity echo canceller has long been recognized as the industry benchmark for DSP-based voice enhancement and echo cancellation.