Abstract: The invention comprises an improved device for selectively authorizing passage through a door. A card reader accessible from each side of the door comprises a path along which the card is moved, terminating at its opposite ends in respective slots with respective card sensors, and a drive system for moving a card in either direction along the path. The device is microprocessor-controlled and is responsive to insertion of a card in a first slot by moving the card to a position beyond a read head. If the signal on the card authorizes access the door is opened and the card is moved to the second slot. If not, the card is returned to the first slot.