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Article theft detection apparatus

  • US 5,245,317 A
  • Filed: 12/18/1991
  • Issued: 09/14/1993
  • Est. Priority Date: 12/18/1991
  • Status: Expired due to Fees
First Claim
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1. An alarm system comprising:

  • a variable transmitter circuit having at least one transducer for emitting inaudible sound waves, the sound waves being varied based on the configuration of an area where an item to be monitored is located and the location of each transducer to substantially saturate said area;

    a security tag having a receiver and an alarm coupled to the receiver, the security tag being attachable to the item to be monitored; and

    the receiver being responsive to the inaudible sound waves and being operative to actuate said alarm to provide an audible signal when the receiver no longer detects the inaudible sound waves.

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