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Binary encoded multiple frequency RF indentification tag

  • US 5,218,189 A
  • Filed: 09/09/1991
  • Issued: 06/08/1993
  • Est. Priority Date: 09/09/1991
  • Status: Expired due to Fees
First Claim
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1. A tag for identifying an associated or attached item comprising:

  • an inductance; and

    a capacitance connected in parallel with the inductance, the capacitance comprising a plurality of individual capacitors, the individual capacitors being connected to establish with the inductance a first resonant circuit having a first predetermined resonant frequency, each of the individual capacitors having a different value, at least one of the individual capacitors including shorting means for causing said at least one capacitor to become short circuited when the first resonant circuit is exposed to electromagnetic energy at the first resonant frequency at a predetermined power level to establish a second resonant circuit having a second resonant frequency said second resonant frequency being dependent upon the particular individual capacitor which is short circuited;

    wherein each capacitor is capable of being in an active state or a shorted state, the different values determining the bit positions of a binary number uniquely associated with the tag, and the combination of capacitors having active and shorted states establishing the binary number.

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