| 摘要 |
A stepping switch has loads connected to its fixed contacts via limit switches. The loads are energized sequentially as the movable contact of the stepping switch is stepped from fixed contact to fixed contact, dwelling on each fixed contact until the corresponding limit switch is actuated to produce an electrical pulse. Such pulse energizes a stretcher relay coil which both establishes a circuit which independently of the limit switches and the stepping switch contacts, keeps it energized and energizes the step coil of the stepping switch. The stretcher relay coil is energized through a normally-closed snap switch which opens temporarily at the end of a step, and de-energizes the stretcher relay coil which, in turn opens the aforesaid circuit, whereby to de-energize both the step coil and itself.
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