| 摘要 |
<p>The lock includes a half-round latch (6a) moved by a key-operated mechanism attached to a pivot below the latch. The latch lies between a base plate (13) and a back plate (10), the back plate being attached to the support which carries the square shaft of the door handle (8). A recessed part (10a) of the back plate normally lies adjacent to the curved surface of the latch. A switch (14) lies between the back plate (10a) and a support (12) which is attached to the base (13). Connection wires (15) link this to an alarm circuit. If the door is forced, then the latch pin moves at right angles to its axis, lifting the back plate (10a). This in turn removes the pressure on the switch which normally maintains the contacts closed. This switch change serves as the signal to actuate the alarm.</p> |
