| 摘要 |
In an information access system, an active-type contactless information storage device senses a carrier of an RF signal at a first frequency in time periods for carrier sensing occurring in a predetermined carrier sensing cycle period, and then in response to detection of a carrier of an RF signal at the first frequency, further receives the information request signal, while it also transmits the tag information signal at a second frequency carrying information in time periods for tag information transmission occurring in a predetermined tag information transmitting cycle period. A reader/writer device cyclically transmits an information request signal carrying values of the predetermined carrier sensing cycle period and the predetermined tag information transmitting cycle period, at a first frequency during a predetermined period of time for information request transmission, and in response to reception of a tag information signal at the second frequency, reproduces and compares received tag information with a list of tag information. In response to reception of the information request signal, the active-type contactless information storage device reproduces and sets the values of the two predetermined cycle periods into its respective timers. Thus the active-type contactless information storage device reduces its power consumption.
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