3-Way Switch Explained
The 3 way switch was originally developed to allow users to control a light from two different locations. This requires a special switch. A regular switch has only two connections and simply cuts the flow of electricity through the switch or allows the current to pass through it. Three way switches each have three connections and are used in tandem. Rather than stopping the flow of electricity within them, they channel the electricity to one connector or the other.
Our diagram, above, is animated. It has four frames to show all the possibilities between two switches and shows the results of these possibilities. Each frame is five seconds long to allow you to familiarize yourself with the flow of electricity before the next frame. The red line shows where the current is flowing. The black lines show where the current is not flowing, but connections exist. The gray line leading to "neutral" can be thought of as the white wire in your circuit.
Every frame on the diagram represents the flick of one or the other of the toggles. Note that the wires outside the switches remain constantly in place. It is only within the switch itself that the flow gets changed. Thus we see that a flick of either switch will change the state of the light to its opposite from any of the four possibilities.