| 摘要 |
<p>The cash or cheque card (11) consists of two plastic cards (12, 13) between which are encased an aluminium sheet (14) in which coded holes (20) are punched and a covering paper sheet (18) carrying information which can be read through the transparent top plastic sheet (12). In addition, two rows of infrared band pass filters (15, 16) are mounted between the plastic sheets (12, 13). A modulated wideband infrared transmitter (40) directs a beam through an array of filters (43, 44, 45) through the card and through the filters in it. The outputs are received (46, 47, 48), fed through further filters set at the modulation frequency, typically 10 KHz, rectified (50, 55, 56) and compared (52, 54) to detect whether the filter array is correct, and so whether the card is genuine.</p> |
