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Echo suppressor having self-adaptive means

  • US 4,012,603 A
  • Filed: 08/22/1975
  • Issued: 03/15/1977
  • Est. Priority Date: 08/27/1974
  • Status: Expired due to Term
First Claim
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1. An echo suppressor for use in a communications network coupling a calling subscriber to a called subscriber comprising a four-wire circuit having an input path for incoming signals from the calling subscriber and an output path for outgoing signals from the called to the calling subscriber, a two-wire circuit coupled to the called subscriber;

  • hybrid means coupled between said two-wire circuit and said four-wire circuit to provide impedance balance between said circuits;

    the improvement comprising;

    first means coupled to input and output paths for generating a first signal representative of the ratio of the level of the incoming signal to that of the outgoing signal both of said levels being obtained over periods of time which are mutually different but are at least partly overlapping;

    second means coupled to said first means for generating a second signal representative of the product of said first signal and the level of the incoming signal obtained at a point in time after the first signal is generated;

    third means coupled to said output path and said second means for detecting the called subscriber'"'"'s signal by comparing the outgoing signal level with the level of said second signal;

    fourth means coupled to said input path for detecting the calling subscriber'"'"'s signal to generate an output;

    fifth means coupled to said third and fourth means for generating a third signal only during the presence of the output of said fourth means and the absence of the output of said third means; and

    sixth means disposed in said output path and responsive to the output of the fifth means for disconnecting the output path to prevent an outgoing signal from being transmitted to the four-wire circuit during the presence of said third signal.

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