| 摘要 |
The invention relates to an electronic circuit making it possible to detect the very low frequency signals set up either by the sudden opening of a door or window or by a perimeter break-in of any kind. The device, according to the invention, consists of a microphone-type sensor 1 of an adjustable high-gain amplifier 2, of a very low frequency-low frequency converter 3 which rejects any electrical signals other than the very low frequency used for the detection of the perimeter break-in, of a second amplifier 6 making it possible to drive an integrator 7 which will control the output interface 8 which may be linked to any external alarm device. <IMAGE>
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