| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-cost burglar prevention device capable of detecting that an outer wall, a glass plate or the like that is a watch target is broken or bored, with high accuracy. SOLUTION: This burglar prevention device has speakers 2 provided in a space on one side of a boundary face 20, each outputting a prescribed detection sound wave; microphones 3 provided in a space on the other side, each detecting the detection sound wave; and a detection means 5 giving an alarm when an output intensity of the microphone 3 exceeds a prescribed level.
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