| 摘要 |
The device comprises a flat and elongated condenser with a piezoelectric dielectric material placed between two electrodes. This condenser is fastened to a barrier surface such as the glass pane of a display, a cupboard, a glass pane which delimits a protected space. The condenser is connected with an electrometric amplifier, the signals of which are transmitted to an electronic alarm unit. When the glass pane is submitted to shocks or to mechanical stresses due to an attempted break-in, the condenser will generate electrical signals able to trigger an alarm when they exceed a certain threshold. The condenser and the amplifier may also be adjusted so as to trigger an alarm when the electrical field is modified by the movements of a dielectrical body within the protected region.
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