Shielding field method and apparatus

  • US 5,253,162 A
  • Filed: 05/17/1990
  • Issued: 10/12/1993
  • Est. Priority Date: 05/17/1990
  • Status: Expired due to Term
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First Claim
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1. A method for selective communication between a stationary transmitting device and at least a selected one of a plurality of mobile responding device, the method comprising the steps ofgenerating from said stationary transmitting device a first field of radiated electromagnetic energy, said generating step including the step of encoding said first field with a first signal intelligible to said responding devices, said first signal being representative of a request to execute a selected operation,directing said first field at said at least one selected responding device,generating from said stationary transmitter a second field of radiated electromagnetic energy, said second field being effective at any responding device within said second field to blank out said first signal, and directing said second field at others of said plurality of responding devices, whereby said others of said plurality of responding devices are prevented from receiving said first instruction.

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