| 摘要 |
The invention relates to a method and to a device for checking security documents. According to this method, which uses a known capacitive coupling, the electrical signals are transmitted by transmitting antennae (8) via security features to receiving antennae (9), the receiving signals being then amplified. The time and amplitude variations of the amplified signals are then evaluated and compared with existing known signal variations, being converted into signal variations representing easily comparable parameters. In order to enable the specific selectivity of the checking device, a selective amplifier (14) is added to the evaluating electronic arrangement. The currency specific definition by means of the evaluating electronic arrangement is achieved for example by using a controller to determine a time limit where an amplitude variation is present, this time being different from the duration of the amplitude variations of all the other currencies.
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