| 摘要 |
A card-operated parking system utilizes cards having a succession of discrete filtered light transmitting areas thereon. The cards operate a card reader which includes a light source and light sensing means, between which the card is inserted, and a punch which punches out a filter area after it has triggered the time-dispensing mechanism. The filters transmit light having a photon energy below a level characteristic of the filter material but absorb light having a photon energy above that level. Two light sensors are positioned in the light path, one receptive to light of the first mentioned photon energy and the other to light of the second photon energy. Only the outputs corresponding to filtered light trigger the parking time dispensing mechanism. The light source may be a tungsten filament bulb or a pair of light emitting diodes of different photon energies. The light sensing means may be a pair of photodiodes or a pair of phototransistors.
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