Object tracking

  • US 6,989,741 B2
  • Filed: 08/07/2002
  • Issued: 01/24/2006
  • Est. Priority Date: 08/07/2002
  • Status: Expired due to Fees
First Claim
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1. A method of locating objects, comprising the steps of:

  • attaching an E-tag to each object, each E-tag having a unique ID associated with the object to which the E-tag is attached, each E-tag adapted to receive a LF carrier signal, each E-tag adapted to receive a HF carrier signal, each E-tag adapted to determine whether a received LF carrier signal contains the E-tag'"'"'s unique ID, each E-tag adapted to determine whether a received HF carrier signal contains the E-tag'"'"'s unique ID, each E-tag adapted to transmit a response signal indicating a LF carrier signal was received, and each E-tag adapted to transmit a response signal indicating a HF carrier signal was received;

    transmitting a LF carrier signal containing the unique ID associated with an object to be located;

    transmitting a first response signal from any E-tag that receives a LF carrier signal containing the E-tag'"'"'s unique ID, the first response signal indicating that a LF carrier signal was received;

    checking whether a first response signal is received;

    transmitting a HF carrier signal containing the unique ID contained in the transmitted LF carrier signal if no first response signal is received;

    transmitting a second response signal from any E-tag that receives a HF carrier signal containing the E-tag'"'"'s unique ID, the second response signal indicating that a HF carrier signal was received; and

    checking whether a second response signal is received.

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