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Transponder system with variable frequency transmission

  • US 5,450,492 A
  • Filed: 10/30/1992
  • Issued: 09/12/1995
  • Est. Priority Date: 05/01/1990
  • Status: Expired due to Term
First Claim
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1. An electronic identification system comprising:

  • a) means for generating an electromagnetic excitation field at a first frequency settable to a plurality of different frequencies;

    b) portable transponder means including means for storing variable identification data, and means for detecting ingress of said portable transponder means into said electromagnetic excitation field and in response transmitting at a second frequency settable to a plurality of different frequencies an informational signal containing said data, said transmitting of said signal being independent of said transponder means remaining in said field, said second frequency being neither derived from nor related to said first frequency of the electromagnetic excitation field, and said first and second frequencies remaining constant during transmission of said information signal; and

    c) means for receiving said informational signal and in response generating an output signal representing said variable identification data contained in said informational signal.

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