Staircase wiring 2

You have here a 3-way circuit, common in house wiring where 2 switches are needed to control a single device.

Here is a simpler version, and also a demonstration of a 4-way circuit as well.http://everycircuit.com/circuit/5354599383564288

Heads up, most call it 2 way and 3 way, in america we call it 3 way and 4 way. I look at it like road intetersection.

Two switches at two doors is a two way. There are two ways out of the room and they are far away from each other, and this is a totaly dark room. Another picture is: A staircase, one switch downstairs and one upstairs. Two ways. The number of ways has nothing todo with the number of electric contact points seen at switches. Anyway, the values 3,4 (one might think of 8 with DC current we might declare a way as forward and backward journey as different ways, if we watch the way of current to travel a way, again nonsense) 3&4 are so hardly wrong programed into millions of heads, no chance to get it out and you have to silently accept this nonsense as "ok". Actually its even less then a two way if we ignore the direction again, cause a tunnel or a simple staircase is only 1 way with two endpoints ;-)