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Identification system

  • US 4,730,188 A
  • Filed: 12/30/1985
  • Issued: 03/08/1988
  • Est. Priority Date: 02/15/1984
  • Status: Expired due to Term
First Claim
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1. An object identification system, comprising:

  • an interrogator comprising means for sending a continuous interrogation signal and means for detecting a responsive identification signal, anda transponder comprising means for detecting said interrogation signal and for transmitting an identification signal in response to said detection,wherein said identification signal extends over a plurality of bit cells of equal length in time, and comprises a preamble portion having a specified number of bit cells and an identification portion having a specified number of bit cells, and a further encoded portion having a specified number of bit cells having a predetermined signal content interposed between said preamble portion and said identification portion; and

    wherein said preamble and identification portions of said identification signal are transmitted according to a first format in which a signal transmission parameter is varied between first and second values during each of said bit cells, and wherein said further encoded portion is transmitted according to a second format in which said identification signal is transmitted without variation in said transmission parameter for a period at least equal to one bit cell.

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