| 摘要 |
<p>An alarm system uses seismic vibration detectors (geophones) for detecting the movement of persons or vehicles in an area. Adjacent groups of one or more detectors in an array are connected respectively to two separate wiring circuits which are connected to alarm output means, adjacent groups of detectors in each wiring circuit being connected in anti-phase with each other. Electrical means suppresses signals outside a predetermined vibration pattern.</p> |
