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Apparatus and method for delivering power to a contactless portable data device

  • US 5,905,372 A
  • Filed: 12/17/1997
  • Issued: 05/18/1999
  • Est. Priority Date: 12/17/1997
  • Status: Expired due to Term
First Claim
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1. In a terminal device, a method of powering a portable data device comprising the steps of:

  • transmitting to the portable data device, in a first mode of operation, a power signal at a first power level and a data signal using a first modulation format and a first bit rate;

    transmitting to the portable data device, in a second mode of operation, a power signal at a second power level and a data signal using a second modulation format and a second bit rate;

    determining a power requirement from the portable data device to change modes of operation from the first mode of operation to the second mode of operation; and

    changing, responsive to the step of determining, between the first mode of operation and the second mode of operation,where the second power level does not equal the first power level.

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