| 摘要 |
A magnetically-actuated sensing device for use in security monitoring systems. A switch unit having a plurality of electrically interconnected magnetic reed switches disposed in a predetermined physical relationship is provided for controlling electrical circuits. Each reed switch is biased in a magnetically-actuated state by permanent biasing magnet in close proximity thereto, the biasing magnets being arranged in a predetermined combination of polarity orientations. A corresponding number of permanent actuating magnets with polarity orientators opposing those of the biasing magnets are disposed within an actuating unit so that they overcome the effect of the biasing magnets when the switch unit and actuating unit are in a predetermined physical relationship with each other. The polarity of at least one of the biasing magnets opposes the polarity of other biasing magnets of the device, providing a sensing device which cannot be deceived using only a single permanent magnet to simulate the actuating magnets. Single-pole-double-throw reed switches may be used to give positive signals corresponding to both alignment and misalignment of the actuating unit with the switch unit. Magnetic shielding associated with the switches and actuating magnets allows the device to be factory-adjusted and sealed, and thereafter to be used in environments containing magnetic material without further adjustment.
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