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Intruder detection system with false-alarm-minimizing circuitry

  • US 4,764,755 A
  • Filed: 07/27/1987
  • Issued: 08/16/1988
  • Est. Priority Date: 07/27/1987
  • Status: Expired due to Term
First Claim
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1. An intruder detection system comprising:

  • (a) sensing means for sensing the presence of an intruder in a region under surveillance, said sensing means being adapted to produce a first output signal which changes in level in response to the presence of an intruder in such region;

    (b) pulse generating means for producing pulses of current each time said first output signal exceeds or falls below a preset threshold level;

    (c) integrating means, operatively coupled to said pulse generating means, for integrating said current pulses and for providing a second output signal representative of the integrated value of such pulses;

    (d) threshold sensing means for producing an alarm signal in the event said second output signal exceeds a predetermined level; and

    (e) timing circuit means for discharging said integrating means in the event said second output signal fails to exceed said predetermined level within a preselected time interval, said time interval being reset (i.e. re-established) each time said first output signal exceeds or falls below said preset threshold level.

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