| 摘要 |
Positive assurance of correct connection, in supplying electrical utilization equipment from a current source, is provided when it is critical to safety and particularly when receptacle outlets are used or a fixed wiring installation required which may be subject to wiring error. An electromagnetic relay is employed to prevent equipment use and to provide audible indication in the event of hazardous connective error such as reversal of ungrounded and grounded neutral conductors and the omission of a grounding connection. The relay may be one that is also otherwise controlled for on-off power switching.
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