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Method of enabling two-state operation of electronic toll collection system

  • US 7,388,501 B2
  • Filed: 05/19/2006
  • Issued: 06/17/2008
  • Est. Priority Date: 05/19/2006
  • Status: Expired due to Fees
First Claim
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1. A method for determining a state of a transponder, the transponder having at least a first state of operation and a second state of operation, the transponder including an antenna for propagating RF signals, wherein the RF signals have a first polarization in the first state and the RF signals have a second polarization in the second state, and wherein the first polarization is substantially different from the second polarization, the method comprising the steps of:

  • transmitting an RF polling signal from a reader to the transponder, the reader having a plurality of antennas for propagating the RF polling signal;

    detecting a response signal from the transponder;

    if said response signal has said first polarization, determining that the transponder is in said first state; and

    if said response signal has said second polarization, determining that the transponder is in said second state.

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