I was leaving the bathroom yesterday, and I noticed something that I usually take for granted.  Our bathroom here in my luxurious accomodations at Burton-Conner has not one, but two light switches.  Two light switches.  The curious thing is that regardless of the position of the other switch, flipping one switch will always cause a state transition in the light.  If you think about it, this is actually pretty non-trivial to implement.

I couldn’t think of a simple circuit that would implement the desired behavior.  Clearly, neither putting the switches in series nor putting them in parallel would work.

The strange thing is, after observing the behavior of the switches for a while (much to the bewilderment of my suitemates), I realized that the state of the light was a simple XOR of the positions of the switches.  My bathroom has an XOR gate built in to it.  I wonder what would happen if I somehow “wired” together enough bathrooms.  Could I make arbitrary combinational logic circuits?  I’d need one other type of gate…