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Proximity detecting apparatus

  • US 5,099,227 A
  • Filed: 12/18/1989
  • Issued: 03/24/1992
  • Est. Priority Date: 07/18/1989
  • Status: Expired due to Term
First Claim
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1. A remotely powered batteryless portable device having circuitry for storing and transmitting coded information comprising:

  • a memory in which coded information is stored;

    electromagnetic coupling means for receiving electromagnetic radiation of a first predetermined frequency;

    power means connected to said first coupling means for deriving power from the received signal for use by the circuitry in said portable device;

    circuit means, connected to said first coupling means and responsive to a received signal of said first predetermined frequency, for reading said coded information from said memory;

    means for generating a carrier signal of a second predetermined frequency;

    modulating means for modulating said carrier signal with the coded information read from said memory;

    electrostatic coupling means, connected to the output of said modulating means, for transmitting the modulated carrier signal via an electric field; and

    further means, connected to said output of said modulating means, for simultaneously causing said modulated carrier signal to be electromagnetically transmitted.

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