| 摘要 |
The alarm has a P-shaped casing (1) of metal or reinforced plastic material. An aperture is made in the casing to allow insertion of a contact switch. The casing houses a 9V battery connected to a contact, a loudspeaker and a printed circuit. Withdrawal of the contact button from its aperture leaves the contact free which actuates the alarm if a bolt, once retracted, is not reinserted within 10 seconds. The alarm can be deactivated only by reinsertion of the contact switch in its aperture.
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