| 摘要 |
A burglar alarm system is mounted in a doorway framing which comprises a reinforcement metal plate extending over a substantial portion of the wall studs and a substantial portion of one minor face of the door jamb, which plate is securely affixed to the wall stud and the minor door jamb face to cover a substantial region of the minor door jamb face adjacent and beyond the door latch bolt hole in the side rail. The alarm system comprises a pair of elongated copper sheets insulated from the metal plate and arranged between the plate and the minor door jamb face. The copper sheets extend side-by-side along a major portion of the reinforcement plate and are insulated from each other. The copper sheets are connected to an electric control circuit energizable to set off a burglar alarm and energized upon electrical contact being made by the sheets through a metal burglar tool used in an attempt to jimmy the door.
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