| 摘要 |
Apparatus is provided for determining when a weight has been lifted from a specific location. It is especially useful for sounding an alarm when an invalid patient attempts to get up from a chair or a bed. The apparatus comprises a very thin sealed reed switch affixed near the bottom of a compressible pad and a magnet affixed near the top of the pad, the reed switch being connected in an electrical circuit containing an alarm mechanism such that, when the pad is compressed and the magnet is in close proximity to the reed switch, the circuit is open and no alarm sounds, but when the weight causing the compression of the pad is lifted, the circuit closes and the alarm sounds. When a battery is used to power the electronics in a preferred embodiment, no power is drained in this system in use until the weight is removed, the life of the battery thereby approximating its shelf life. Time delays between lifting of the weight and sounding of the alarm can be provided by varying the compressibility of the pad or by providing an electronic time delay. A normally closed reed switch may be used or a normally open reed switch may be used.
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