| 摘要 |
<p>There is a lock release apparatus for providing delayed passage past a movable barrier such as an exit door which is held to a closed position by a lock. The apparatus includes a beam transmitter, a beam receiver, a timer for releasing the lock after a predetermined delay, a trigger associated with the timer and a beam reflector affixed to an operating bar on the movable barrier. In use of the apparatus when the barrier is closed and locked the transmitter directs a beam onto the reflector at an orientation such that reflection is detected by the beam receiver when the operating bar is undisturbed. Subsequent movement of the operating bar to open the barrier terminates or shifts the reflection away from the receiver to trigger the timer to release the lock after the predetermined delay.</p> |
