I know about circuits and a single switch. But the multiple light switches really confuse me. They don’t have a set position for off and on. They essentially reverse the state of the light bulb. So how do they work?
In: Engineering
In this case, you can think of electricity like a train on a train track. Pretend you have two tracks, side by side (a North one and a South one, for example). A train is traveling on the north track, headed for the depot. On the journey, there are some switches which can alter the trains path. If the switches are off, the train keeps travelling on the north track, but if they’re on, the train is redirected onto the south track. In essence, the switch makes the train “switch” tracks.
If you flip the first switch, the train moves onto the south track. It’s gonna miss the depot. However, if you flip another one further down the path, the train goes back to the north track and is on route to the depot. As long as the switches are flipped on or off to cancel each other out, there’s nothing to worry about.
In the analogy, the train is the electric current, and the depot is the bulb. Switches redirect the electricity, but as long as they cancel out, then the light stays on.
/u/jammin-john is exactly right. For the visual learners, though, [here’s a good wiring diagram](https://en.wikipedia.org/wiki/Multiway_switching#/media/File:3-way_switches_position_2.svg) for circuits with two SPDT switches. Using DPDT switches, you can have [three or more switches]( https://en.wikipedia.org/wiki/Multiway_switching#Traveler_system_2) serving the same circuit, any one of which can reverse the state of the light.
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