| 摘要 |
<p>PURPOSE: To detect an illegal behavior by detecting an AC signal appearing in a circuit due to the influence of capacitive connection between an unnecessary lead wire extending through the conductor element and the conductor element. CONSTITUTION: When a forged card 40 is inserted into a reader, one end of the lead wire 46 in the card is electrically connected to one of contact points 26 in the reader and a part of the wire naturally passes through a plate 50. Consequently, an electric circuit constituted by a processing circuit 28, a flexible blade 26, an oscillator 62 and a detector 70 is closed by capacitive connection between the forged lead wire and the plate 50. Thus, the AC signal flows in the circuit, AC voltage is applied to the input 70a of the detector 70 and the signal is transmitted to an alarm circuit through an optical coupler 78. Consequently, the illegal behavior can be detected.</p> |
