| 摘要 |
PCT No. PCT/SE96/01075 Sec. 371 Date Feb. 28, 1998 Sec. 102(e) Date Feb. 28, 1998 PCT Filed Aug. 29, 1996 PCT Pub. No. WO97/08522 PCT Pub. Date Mar. 6, 1997A security system having a vibration detector that senses vibration in any direction is disclosed. The vibration detector includes two or three detector elements that each have a magnet, and a coil or Hall-effect device that produces a signal in response to changes in a magnetic field in the vibration detector caused by movement of a magnet. The magnet in each detector element is mounted for reciprocating movement in one or more planes about a rest position. Each magnet is held temporarily in the rest position by springs. When three elements are used, the magnets are mounted on journalled shafts or on plate-like springs for reciprocal movement in directions that are at right angles to each other. When only two elements are used, the magnets are mounted on an elongate spring of substantially circular cross section so that the axial dimensions of the springs are at right angles to each other for reciprocating movement in all directions along a respective curved surface coinciding with a plane that is perpendicular to the axial dimension of the spring. |
