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Double talk and line noise detector for a echo canceller

  • US 4,645,883 A
  • Filed: 05/09/1984
  • Issued: 02/24/1987
  • Est. Priority Date: 05/09/1984
  • Status: Expired due to Fees
First Claim
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1. An echo canceller for removing echoes propagating from a receive line to a send line through a transmit/receive station, comprising:

  • means for emulating an echo resulting from a signal on a receive line within a station;

    subtracting means for subtracting said emulated echo from a signal on said send line;

    means for measuring an average background noise on an output of said subtracting means;

    a non-linear device connected to said output of said subtracting means for selectively, when enabled, attenuating low level signals on an input of said non-linear device;

    means for selectively injecting onto an output of said non-linear device, when enabled, a noise signal proportional to said measured background noise; and

    means for detecting a signal above a predetermined limit on said receive line and, in response to said detection, for enabling said non-linear device and said injecting means.

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