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Proximity card detection system

  • US 6,535,136 B1
  • Filed: 02/03/1999
  • Issued: 03/18/2003
  • Est. Priority Date: 02/26/1998
  • Status: Expired due to Fees
First Claim
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1. A security system comprisinga card containing access information, a locking mechanism, a circuit coupled to the locking mechanism to operate the locking mechanism if the access information is read by the circuit, the circuit being configured to read the access information contained on the card after the circuit detects first the absence of electromagnetic energy, then the presence of intermittent electromagnetic energy, then the absence of intermittent electromagnetic energy during a preset period of the card being hold adjacent the circuit;

  • and the circuit being configured to determine an amount of time that elapses between detecting the absence of electromagnetic energy and detecting the presence of the intermittent electromagnetic energy and between detecting the presence of the intermittent electromagnetic energy and detecting the absence of the intermittent electromagnetic energy.

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