A card reader includes an opaque arm movable in response to the insertion of a credit card. The arm, when moved, interrupts a light path signalling the presence of the card thus permitting write or read operations on a magnetic stripe on the card. The use of arm permits highly reliable operation due...http://www.google.com.tw/patents/US4742213?utm_source=gb-gplus-share專利 US4742213 - Credit card reading apparatus with reliable optical path interrupt means
