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MOTION SENSOR SYSTEM

  • US 3,777,139 A
  • Filed: 12/03/1970
  • Issued: 12/04/1973
  • Est. Priority Date: 12/03/1970
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting an approaching train within a track section between a feed point and at least one low impedance connection across the rails, said apparatus comprising:

  • transmitter means coupled to the rails at the feed point for applying a current to the track section;

    receiver means coupled to the track section for producing a first signal representative of the impedance of said track section;

    differentiator means, coupled to said receiver means, for producing a second signal representative of the rate of change of said first signal;

    motion detector means, coupled to said differentiator means, for producing a warning signal when said second signal is of a selected polarity and exceeds a preselected magnitude, whereby the presence of a train in the section, approaching the feed point at a speed greater than a preselected speed produces a warning signal;

    low signal detector means coupled to said receiver means for producing a warning signal when said first signal is less than a preselected value, whereby a defect in said track section which causes an abnormally low impedance therein produces a warning signal; and

    track-occupied means, coupled to said low signal detector means and to said motion detector means, for inhibiting said low signal deTector means from producing a warning signal during the time period that a warning signal is produced by said motion detector means and for a preselected time period thereafter.

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