| 摘要 |
The invention relates to an alarm device which gives an alarm signal when the object with which it is associated is moved with respect to its normal position. The device essentially comprises a photoelectric detector-amplifier 10 associated with an electronic alarm circuit 11, the whole being mounted on a plate 23 carried by a support 12 which is placed in proximity to and behind the master plate 13 to be monitored. The detector-amplifier 10 is of the direct-reflection type which supplies an electrical signal when the panel is in place. Removal of the panel gives rise to an alarm signal. The invention is applicable to the surveillance of exhibition galleries, museums, etc. <IMAGE>
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