4-ways

update: I finished wiring this up. Revised wiring diagrams can be found here.

I recently discovered the 4 way. Unfortunately, I mean the light switch instead of something more nudity based. And suddenly I'm wondering how many people it takes to go from a numbered amount of people (i.e. 3-some, 4-some, etc) to an orgy. Mind you, I still find a two-some pretty exotic. But do you have to lose count of the number of people? Does an orgy become a 20-way if someone does a head count... er, cranium count? Is this totally off topic? Yes it is.

If you're wiring up two switches for a light you need a couple of 3-way switches. For more switches you need a 4-way switch.

The way a 4-way switch works is that you have 4 wires attached much like you see in the picture below. There's really a 5th wire, but we're ignoring the ground wire for today's purposes. With the switch one way the current goes across like you see on the left. With the switch the other way, the current crosses over.

Norman's house had an arrangement with two switches and a light at the top of the stairs. We're rewiring that and adding another light down the hall from the first and a switch by that light. To do that we need to wire things up like you see below. 

This next bit shows all the possibly arrangements of these three switches. Green means lights on and red means lights off. So there's no way that I couldn't flip a switch and toggle the two lights in the hall at the top of the stairs. 

You can add a 4th switch by adding even more 4-way switches to the middle of the series of switches. You can have however many switches you want so long as the ones in the middle are all 4 way and 3 way switches cap the ends. Go ahead. Doodle it out. I dare you. 

And no lights go between switches without making things difficult. They all have to go on one side of the power supply or the other.

That seems perfectly simple enough, but what we seem to have already in place in the house is this. 

The power source is unknown. I've run a new for our lights, but the original power source is lost in limbo somewhere. From what I can see, there's a 3-way switch at the bottom of the stairs, and at the top is a 4-way that they're treating like a 3-way, with the 4th wire running off to power other parts of the house. But it doesn't cut off power to anything when the stair lights are on. So I'm really not sure what's going on. But I'm closer than I was two weeks ago.