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Vibration detectors are used to protect against physical attack on the fabric of a building or room.
Structure and working
The piezo-electric crystal sensor in Vibration detection devices produces electrical impulses as soon as it senses vibration or sudden impact. The impulses are formed into a signal and the unit features an integral analyser and sensitivity control.
In an intruder alarm system, the unit requires 12 V dc regulated supply, which is provided by the control panel. The isolated contacts of a energised relay is connected to the alarm output of the detector, which is also used to detect any supply failure to the device.
The imapct detector is usually fitted on doors through which an intruder could attempt to gain entry by forcing out a panel or forcing the door from its hinged side leaving any protecting magnetic reed switches in situ. Thus, the use of impact detector, when complementing reed switches, prevents any attempt to intrude by such means.
Precautionary measures
It is necesssary for the the protected surfaces to be in contact with the base plate with minimum distortion Tapping the protected surface causes the device to go into an alarm mode, indicated by the light emitting diode (LED). An integral sensitivity control can then be adjusted so that the device operates at the desired range of impact response, taking into account environmental conditions.
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