| 摘要 |
PCT No. PCT/SE86/00359 Sec. 371 Date Apr. 20, 1987 Sec. 102(e) Date Apr. 20, 1987 PCT Filed Aug. 8, 1986 PCT Pub. No. WO87/01226 PCT Pub. Date Feb. 26, 1987.A surveillance installation to protect an area of ground. A number of sensing units are spaced around the perimeter of the area to be protected. Each sensing unit comprises a network of strands inconspicuously deployed over a portion of the ground and connected to a magnetically operated switch. When an intruder trips one of the strands, the magnetic switch is operated to signal the presence of an intruder. A central monitoring unit powered by a low voltage D.C. supply connects the various sensing units by means of a two-wire circuit. The central monitoring unit includes signalling devices to indicate the location of the intruder. The system also has the capability of initiating intruder warning devices.
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