Electrical – Need a Switch that Stays Off Once Power is Out


What is the name of an electrical switch that meets the following requirements?

  1. I can plug the switch in between a 120v outlet and my device,
  2. Energizes the device (and stays energized) when I momentarily
    mechanically/physically engage the switch,
  3. De-energizes the device (and stays de-energized) when I momentarily mechanically/physically disengage the switch, and
  4. De-energizes the device and sets the switch to open/off when the outlet loses power.

That is, I want an energized device to be de-energized should the power go out and for the device to stay de-energized should the power come back on. When the outlet's power has been restored, the device will only be (re-)energized (and stay energized) once I momentarily engage some button.

Maybe I am looking for the opposite of an overload fuse/GFI – some "fuse" to trip when the source power is lost and I need to engaged a button to reset it.

I did find that a "relay toggle switch" might possibly describe the type of switch I'm trying to find, but there were so many varieties that I am asking for some assistance from this community to point me in a more focused direction.

Thanks in advance.

Best Answer

You can do it with two buttons and a relay, like so:


simulate this circuit – Schematic created using CircuitLab

This, or something similar, would be inside the "magnetic starter" that @st2000 mentions in his answer.