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ULTRASONIC BURGLAR ALARM SYSTEM

  • US 3,721,972 A
  • Filed: 02/22/1972
  • Issued: 03/20/1973
  • Est. Priority Date: 02/22/1972
  • Status: Expired due to Term
First Claim
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1. A burglar alarm system for warning of intrusion into a protected enclosure comprising;

  • ultrasonic transmitter means, located exteriorly of said protected enclosure, to emit an ultrasonic signal of predetermined frequency;

    interior receiver means, located inside said protected enclosure to receive said ultrasonic signal through any opening in said enclosure;

    detector means connected to said interior receiver means to detect reception of said ultrasonic signal by said interior receiver means, and to emit an alarm actuating signal if said ultrasonic signal is detected;

    alarm means connected to said detector means to sound an alarm upon reception of said alarm actuating signal from said detector means.

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