| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass breakage sensor capable of preventing a malfunction by a radiation noise of radio frequency band. SOLUTION: Vibration of a glass plate is converted to an electric signal in a detection part 1. A conversion part 5 outputs a signal of a frequency corresponding to the difference between a standard frequency close to a natural frequency generated in breakage of the glass plate and the frequency of the output of the detection part 1. A filter part 4 passes a signal of the difference frequency between the natural frequency and the reference frequency of the output of the conversion part 5. A comparison part 2 outputs a breakage detection signal when the output of the filter part 4 is larger than a preset threshold. The natural frequency component of the output of the detection part 1 is converted to a signal of a lower frequency, whereby a signal of radio frequency band can be easily arrested by the filter part 4. Accordingly, the malfunction by the radiation noise of radio frequency band can be prevented. COPYRIGHT: (C)2004,JPO&NCIPI
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