The 4-way circuit is used when you want to control the light or lights from three or more locations. This article and detailed wiring diagram outlines the steps to wiring a typical 4-way switch.
4-Way Switching Circuits
If you understand the logic behind the 3-way circuit, the 4-way will not seem that difficult.
When Do You Need a 4-Way Switch?
The 4-way is used when you want to control the light or lights from two or more locations.
4-Way Switch – NOT To Be Confused With a 2-Pole Switch!
A 4-way switch has four terminals (do not confuse with and purchase a 2-pole switch by mistake).
The 4-way terminals are labeled “In” and “Out” (two of each). The mechanics of this switch are simple, in that they either switch the travellers straight through, or criss-cross them.
To add more than three locations for one set of lights, you would just insert more 4-way switches in between the two 3-ways. The following diagram illustrates the easiest way to connect a 4-way circuit.
NOTE: The picture is a thumbnail – click on it to enlarge it.