Erkennungsmarke

摘要

An ID card includes an electric wave receiver for receiving an electric wave (12) from a main station, a modulator (6) for modulating a received signal in accordance with an SD number, and an electric wave transmitter for transmitting a modulated electric wave signal (13) to the main station. The main station identifies the SD card on the basis of the modulated electric wave signal. The ID card further includes a surface acoustic wave exciting device for coupling the electric wave receiver and the electric wave transmitter through surface acoustic wave on a piezoelectric substrate (2) by means of the modulator and a circuit including a terminating device (3) and a switching element (4) and connected in parallel with the surface acoustic wave exciting device. The switching element is controlled to be turned on and off in accordance with the ID number to control the coupling between the electric wave receiver and the electric wave transmitter.