Weird Switches

Sarah and I spent some time at our new apartment this weekend, moving in some boxes and getting things ready for painting. At some point I realized that something weird was going on with the switches for three overhead lights in the kitchen, bathroom, and the hallway connecting them.



Here is a perfect scale rendering of that part of the apartment:



The lights are labeled A, B, and C; and the switches are W, X, Y, and Z.



Switch Z is actually behind the gas range, and requires slender fingers to operate. When I had first tried it out, it flipped the kitchen light, A, on and off, but then when I tried to turn that light on again later in the afternoon, it didn't appear to do anything.



After some experimentation, we realized that X, Y, and Z were each tied to a specific light, with switch W acting as a "master" switch that can kill them all. In logic terms,

A = W + Z,

B = W + Y, and

C = W + X.

I don't know why someone would set things up that way: either you keep W constantly in the on position and have to reach behind the stove every time you want to use the kitchen, or you keep Z constantly in the on position and have to turn on the kitchen light when you get up to use the bathroom in the middle of the night.