To provide a non-contact ID tag for realizing miniaturization and the extension of the life of a built-in battery, and an entrance monitoring system reducing the power consumption of the ID tag.
An actuation signal is transmitted from a transmitting and receiving device 23 to the ID tag 18 attached to a mobile element 15, upon detection of the mobile element 15 by a sensor 19, and on receiving the actuation signal a CPU in the ID tag 18 shifts from a sleep state to an actuated state to transmit or receive data to or from the transmitting and receiving device 23. After the transmission and reception of the data is finished, the ID tag 18 returns to its initial sleep state after a certain period of time. Thus, the ID tag 18 can be held in the sleep state when it is out of the detection area of the device 23, and the power consumption of the ID tag 18 can be reduced.
AKIBA YASUSHI
HIRATA KATSUHIRO
MITSUTAKE YOSHIO
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