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Electronic identification system

  • US 3,914,762 A
  • Filed: 12/27/1973
  • Issued: 10/21/1975
  • Est. Priority Date: 12/27/1973
  • Status: Expired due to Term
First Claim
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1. A short range detecting and identification system of the type including a transmitter, a receiver, and at least one identification tag remotely situated relative to the transmitter and receiver, said transmitter transmitting electromagnetic energy signals of a predetermined frequency, wherein:

  • said tag comprises;

    a harmonic radiator for deriving from said signals of said predetermined frequency signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver, encoding means, responsive to a clock signal, for modulating said derived harmonically related signals in accordance with a predeterined digital identification code, and timing means, for deriving said clock signal; and

    said receiver comprises;

    first detector means for detecting said modulated harmonically related signal radiated from said tag and generating output signals indicative of the identification code modulation of said radiated signal, and second detector means for sensing the presence of reflected signals of said predetermined frequency whereby the presence of an inoperative tag is sensed.

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