Patent ID: 7821397

Claim:
An information access system for accessing information stored in a contactless information storage device, the information access system comprising: a reader/writer device connected to an information processing apparatus, the reader/writer device including: a first timer, a first memory, a first transmitter unit which is capable of cyclically transmitting an information request signal at a first frequency during a time period for information request transmission, a first receiver unit which is continuously ready to receive an RF signal at a second frequency different from the first frequency, and a first controller which, in response to reception of a tag information signal at the second frequency, reproduces and compares received tag information carried by the tag information signal with a list of tag information in the first memory; and an active-type contactless information storage device including: a second memory, a battery, a second timer which generates a first cycle for transmitting tag information, a third timer which generates a second cycle for sensing a carrier, a second receiver unit which is capable of sensing a carrier of an RF signal at the first frequency for detection, a second transmitter unit which is capable of transmitting a tag information signal at the second frequency, and a second controller which controls the second receiver unit to sense a carrier of an RF signal at the first frequency in time periods for carrier sensing occurring in the second cycle, then in response to detection of a carrier of an RF signal at the first frequency in the second receiver unit, causes the second receiver unit to further receive the information request signal, and which causes the second transmitter unit to transmit the tag information signal at the second frequency carrying information stored in the second memory in time periods for tag information transmission occurring in the first cycle, and which, in response to reception of the information request signal in the second receiver unit, reproduces and processes received information carried by the information request signal, and which controls the second receiver unit to change from an active state to an inactive state in response to non-detection of an RF signal at the first frequency in a particular time period for the carrier sensing in the second receiver unit, and which controls the second transmitter unit to change from an active state to an inactive state in response to an end of a particular time period for the tag information transmission occurring in the first cycle.