How Three-Way Switch Circuits Work -- The Learning Circuit 45

Great explanation of the circuit, Karen! I'm glad to know that I'm not the only one whose bothered by the whole "switch is up but light is off" concept!

Hi Karen,

This is of course possible but it is contrary to traditional function of slide switches. I saw you had one of these switches. Why not take an ohm meter and verify the position for confirmation. I would be fascinated to see the physics of the internal contacts if you are correct.

John

I'm not sure that you're right for this particular switch. Here's a clip from the data sheet. Unless I'm reading it wrong, A is on when 1-2 are connected and B is on when 1-3 are connected. Those pins are on the opposite side of the slide position.

Yes, different cultures and interpretations, same result!

Thanks for replying.

Kind regards.

Hi Donald,

Yep. Here in the US we call the the circuit, with the crossover switch in between, a 4 way switch.  Interesting how the same thing is labeled differently in different countries.

John

Is this what you call 3 way lighting in America?

I would be used to calling this 2 way lighting, and 3 way lighting would have a third intermediate switch between the 2 changeover switches.

Just curious really.

Kind regards.

Hi Karen,

Very nice presentation of the 3-Way switch configuration. At the very end your explanation of the position of the toggle with respect to the closed contacts was correct but the position of the slide switch with respect to the closed contacts is actually the opposite from what you indicated. The contact follows the slide and this means that the closed contact is always on the same side as the slider.

John

Well explained.

Good job.

DAB