| 摘要 |
The alarm has a P-shaped casing (1) made of a metal or reinforced plastic material. The casing has an aperture allowing insertion of a contact switch (2). The casing houses a 9 V battery (5) connected to a contact (3), a loudspeaker (6) and a printed circuit (7). When the bolt (4) is retracted, the contact passes current to the printed circuit and the loudspeaker thus actuating the alarm after 10 seconds. the printed circuit is designed to remain active with the bolt home until the contact switch is inserted in the aperture. If the switch is withdrawn with the bolt retracted, an immediate alarm is given.
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