Method of detecting narrow-band signals in an echo canceller

Details Method of detecting narrow-band signals in an echo canceller Method of detecting narrow-band signals in an echo canceller

1995-09-15

1997-11-18

Zele, Krista M.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379 3, 379406, 379386, 370286, 370287, H04B 323

Patent

active

056895569

ABSTRACT:
A method of detecting narrow-band signals in an echo canceller to control the coefficient update process, echo suppression process, and the disablement of the echo canceller is provided. The method includes the steps of searching for the presence of a generic tone, searching for DTMF tones, searching for a 2100 Hz tone and, if a generic tone is found, searching for a dial tone. If a generic tone is detected on the far end signal, a tone flag is set which triggers the disablement of the echo canceller coefficient update process and the enablement of the echo suppressor process. If a 2100 Hz tone is detected, the echo canceller is disabled. If a DTMF signal is detected, DTMF flags are set which are used by the echo suppressor for suppressing the near end echo. Finally, if a dial tone is detected, dial tone flags are set which cause the disablement of the echo suppressor.

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