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Child safety device

  • US 6,650,241 B2
  • Filed: 12/22/2000
  • Issued: 11/18/2003
  • Est. Priority Date: 12/23/1999
  • Status: Expired due to Fees
First Claim
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1. A perimeter monitoring system for detecting and monitoring the presence of at least one monitored device within at least one perimeter, comprising:

  • said at least one monitored device comprising;

    a transmitter having;

    an identification generator for providing a unique identification stream corresponding to said transmitter;

    a random interval generator for minimizing collisions of concurrent transmissions from multiple montiored device by aperiodically activating said identification generator at random intervals; and

    an RF upconverter and at least one antenna for transmitting said unique identification stream as a unique identification signal at the random intervals; and

    a receiver for detecting at least one monitored device having;

    a loop antenna with a conductor situated along at least one perimeter forming the loop;

    an RF downconverter for receiving said transmitted signal from the antenna and outputting said unique identification stream;

    an identification decoder for detecting said unique identification stream;

    at least one timer responsive to said identification decoder and associated with said unique identification stream; and

    a timeout detector;

    whereby said timer is reinitialized upon the receipt of said identification stream and said timeout detector produces an alarm signal when said timer reaches a predetermined threshold as an indication that said at least one monitored device is no longer within said at least one perimeter.

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