Many homes have three way electrical circuits to turn on and off lights in two different locations. These electrical circuits are called three-way circuits. Although not as common as three-way electrical circuits for control turning on and off light fixtures, there are also four-way electrical circuits.

Very often three-way and four-way electrical circuits are not understood by DIY homeowners because of the seemingly complex wiring involved. Actually they are quite simple once you understand the wiring.

A three-way circuit is a lighting circuit that allows one light fixture (light or other appliance) to be controlled by two switches in different locations. Stairwells, hallways, and large rooms with multiple access points often have three-way circuits.

There are also four-way and five-way circuits. These circuits are designed using four four-way switches between two three-way switches. For example, a circuit with 4 switches controlling one fixture is not uncommon in large rooms with multiple access points. They are wire with two three-way switches and two four-way switches in the circuit.

The heart of a three-way circuit is the 3 way switch. Unlike a common wall switch that has two active terminals, the 3 way switch has three active terminals (plus a ground).

The three-way and four-way electrical circuits have a three wire Romex cable that run between the switches to control the power to the light fixture. The three wires are red, black, white and a common copper ground wire.

In addition to a ground terminal, each switch has three terminals, a brass colored terminal, a silver colored terminal and black colored terminal. The black wire provides for power to run between the switches and is connected to the switch terminal that is color coded black. The red and white are power carriers that actually control the power going to the light from either one of the two three-way switches and are connect to either the silver or brass colored terminals, it does matter which of these terminals they are connected to as they only serve as carriers.

When replacing a three-way or four-way switch, wire the replacement switch exactly in the same way as the old switch was.

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