Automatic door-locking system - permits entry only to card holders, but does not restrict exit, and uses microswitches to control locking mechanisms

摘要

This door-locking system is of the type which allows access only to persons who insert a coded plastic card into a slot. When the card has been recognised, the mortise part of the night-lock is freed, allowing the visitor to open the door by operating the handle and thus the catch. When the card reader recognises a valid card it transmits a pulse to the input (17) of the lock circuit. The pulse switches on a transistor (19) which allows a capacitor (20) to discharge through the mortise freeing a solenoid (21). The solenoid is kept energised until a microswitch (26) indicates that the visitor has opened the door. The mechanical construction of the lock is such that operation of the inner handle overrides the card reader by means of another microswitch (3), allowing a visitor to leave. However, operation of the outer handle does not operate this microswitch.