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Information access system, information storage device and reader/writer device

  • US 8,587,413 B2
  • Filed: 04/30/2009
  • Issued: 11/19/2013
  • Est. Priority Date: 07/29/2008
  • Status: Active Grant
First Claim
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1. An information access system comprising:

  • a reader/writer device including;

    a first memory,a first timing generator configured to measure time,a first transmitter unit configured to transmit an information request signal at a first frequency in a transmission time period,a first receiver unit configured to receive a response signal at a second frequency which is different from the first frequency, anda first control configured to cause the first transmitter unit to suspend its transmission in a non-transmission time period; and

    an information storage device including;

    a second memory configured to store an identification,a second timing generator configured to measure time,a battery,a second receiver unit configured to sense a carrier of an RF signal at a first frequency for detection, in a first time period that occurs at time intervals, and further receive the information request signal in response to detection of a carrier of an RF signal at the first frequency, and to sense a carrier of an RF signal at the second frequency in response to reception of the information request signal,a second control configured to cause the second receiver unit to sense a carrier of an RF signal at the first frequency for detection, in a second time period after a sleep time period which is shorter than the time interval, in response to determination of non-detection by the second receiver unit of a carrier of an RF signal at the first frequency in the first time period, wherein the shorter sleep time period and the subsequent sensing of a carrier of an RF signal at the first frequency are repeated during the time interval unless a carrier of an RF signal at the first frequency is detected as long as a count of determination of the non-detection of a carrier of an RF signal at the first frequency is smaller than a maximum count threshold, and wherein further sensing of a carrier of an RF signal at the first frequency is inhibited during a remaining time period of the time interval when the count of determination is equal to the maximum count threshold, anda second transmitter unit configured to transmit the response signal at the second frequency in response to reception of the information request signal and in response to determination of non-detection by the second receiver unit of a carrier of an RF signal at the second frequency in the first time period.

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