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 ?
In 2007, ClearOne named Biamp Systems as co-defendant in a suit claiming that it knowingly licensed an acoustic echo cancelling algorithm from a third party that ClearOne alleges was stolen from them.
The system uses the latest noise suppression, acoustic echo cancelling, and dynamic compression techniques and algorithms to deliver clear-speech audio for both crew members and customers.
The sale includes exclusive manufacturing rights and technology license for "large room" acoustic echo cancelling for video and teleconferencing applications.

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