| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass break detecting circuit which is lower in height, lighter, and more inexpensive compared with a conventional circuit. SOLUTION: The circuit is operated by using: a piezo-electric ceramic 111 for outputting an electric signal in sympathetic vibration with the ultrasonic wave of a specified ultrasonic wave frequency band which is generated when glass is broken; a frequency component detecting circuit (113) for detecting a signal with a specified frequency component from the electric signal; and an amplifier circuit (Tr1) for amplifying the output of the frequency component detecting circuit. Till the frequency component detecting circuit (113) detects the signal with the specified frequency component and a detecting signal generating circuit 115 outputs a detection signal, an output level control circuit 112 restricts the output of the piezo-electric ceramic 111, and releases the restriction of the output of the piezo-electric ceramic 111 when the detection signal is inputted. COPYRIGHT: (C)2007,JPO&INPIT
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