Patent ID: 8587413
Filing Date: 2013-11-19
Classification: G06K

Abstract:
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, and a 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, and a 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.