Three-way electrical wiring makes it possible to control a single electronic receptacle (or group of receptacles) from two different locations. This type of wiring is commonly used in residential spaces to control lighting.
Three-way wiring, which involves three-way switches, is convenient when a homeowner wishes to operate a light from both the top and the bottom of a flight of stairs or from two entrances to a room. Unlike switches that are typically flipped upward in order to turn a light on and downward in order to turn it off, three-way switches can be flipped either way, and their function depends on the device they activate. If, for instance, a light is illuminated while one of the two controlling switches is in the downward position, turning the switch upward shuts the light off.
There is no single method for wiring three-way switches. While there is a conventional method, variations are also a possibility. On a basic level, three-way switches differ in appearance from conventional switches by the number of screws that form connections to the various wires. Traditional single-pole switches have two of these screws, while three-way switches have three. One side of the switch has two screws (the common terminal and the traveler) on which the wires can connect, while the other side has a single screw (the other traveler).