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Intruder detector apparatus

  • US 4,602,246 A
  • Filed: 04/08/1985
  • Issued: 07/22/1986
  • Est. Priority Date: 02/11/1982
  • Status: Expired due to Term
First Claim
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1. A detection device for sensing motion, comprising:

  • means for generating an electromagnetic field;

    capacitance means associated with said generating means responsive to disturbances of said electromagnetic field;

    self-excited oscillator means connected to said capacitance means and operative for providing a signal having a frequency which varies in response to disturbances in said electromagnetic field;

    frequency change detector means connected to receive said variable frequency signals from said oscillator and operative to provide an output signal upon detection of changes in said frequency, and including means for suppressing output upon detection of repetitive oscillations of the frequency value; and

    discriminating means connected to receive the output of said frequency change detector, and operative for providing an output signal upon occurrence of a predetermined number of outputs of said frequency change detector means within a predetermined time interval.

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