| 摘要 |
PROBLEM TO BE SOLVED: To suppress useless power sending and to reduce noise on the receiving side by changing the intensity of an electromagnetic wave sent from an interrogator to a non-contact IC card in accordance with two modes, i.e., a transmission mode and a stand-by mode. SOLUTION: When the non-contact IC card exists within a regulated communication distance from the interrogator, an unmodulated wave 11 for driving a switch circuit is intermittently sent from the interrogator by intensity capable of driving the switch circuit preferably at a fixed interval. The card detects the wave 11, turns on the switching circuit and transmits a signal 21 for informing of the communication mode of the card to the interrogator. The interrogator receiving the signal 21 stops the sending of the wave 11, sends an information signal wave 12 by an output level allowed to be detected by the card, after receiving an information signal wave 22 from the card, starts actual communication. When the interrogator ends the communication or the card sends a communication end signal 23, the sending of an unmodulated wave 11 to a succeeding card is started. |
