发明名称 |
Improvements relating to security alarm systems. |
摘要 |
An alarm system uses piezo-electric crystals (2) which when vibrated produce an electrical signal that is used to generate an alarm. Each crystal is in a sensor unit (1) with a latch circuit (13) and an indicator (15), and the threshold at which the alarm triggers latch-on and activates the indicator is adjustable. The latched-on alarm signal in normal use is passed by cable to a remote control module (21), where the actual alarm can be raised. For setting up, the sensor is provided with a periodic power supply from the control module and the alarms (24, 29) are disabled, so that during power-on periods an operator can adjust the sensor threshold without disturbance at the control module. If latching occurs at the wrong level, the subsequent momentary power-off restores the sensor to its primed state, enabling re-adjustment. As well as being responsive to sensor vibration above a set level, an alarm is raised if the cable circuit is broken or short circuited.
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申请公布号 |
EP0044725(A2) |
申请公布日期 |
1982.01.27 |
申请号 |
EP19810303291 |
申请日期 |
1981.07.17 |
申请人 |
YOUENS, JACK;WEYRAD (ELECTRONICS) LTD |
发明人 |
YOUENS, JACK;WHITE, RODNEY EDWARD CHARLES;TIZARD, DAVID JOHN |
分类号 |
G08B13/12;G08B13/16;(IPC1-7):G08B13/12 |
主分类号 |
G08B13/12 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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