| 摘要 |
A plug-type alarm switch for supervision of handwheel water valves and the like has an enclosure having a key-locked cover and containing, wired in series, a two-connector female receptacle and a normally closed enclosure cover tamper switch. The receptacle, otherwise movable within the enclosure, is held in place on being mated through a passage in the enclosure wall to a two-prong male plug, which is shorted by an insulated loop of wire passed through the handwheel. If the handwheel is turned, pulling the loop, the plug and receptacle are unmated, opening the switch circuit and signalling an alarm. The unmated receptacle will not remain aligned with the passage for reinsertion of the plug prongs; to restore the circuit the cover must be unlocked and removed and the receptacle must be physically held in proper alignment as the plug is reinserted.
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