Sounds like three way switches, which IIRC are supposed to have two wires running between them, where one of those two wires isn't connected.

The basic idea is that if switch A is in one position then power flows down one wire, and if switch B is in the same position (connected to that wire) then things light up (or burn, or whatever) and if both switches are in the other position then power flows down the other wire. If the switches are in different positions then power is going down one wire but the other switch isn't connected to that wire. You get the idea.

Get a good electrician or at least feed drinks to one and ask them all the important safety questions, of course.


M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8