What is a two-way light switch and how does it work?
Quick answer
A two-way switch lets you control one light from two different locations — common on stairs and hallways so you can switch a light on at the bottom and off at the top.
🏠Homeowner view
A two-way switching system uses two switches to control the same light — one at each end of a hallway, at the top and bottom of stairs, or either side of a large room. You can turn the light on at one switch and off at the other. Both switches are physically identical and labelled "two-way" — you cannot use an ordinary one-way switch in a two-way circuit. The wiring between the two switches uses a three-core cable (with red, yellow, and blue conductors in older cable, or brown, black, and grey in modern installations). If you want to control a light from three or more locations (e.g. a large living room with three doors), you need a "three-way" or intermediate switch in addition to the two two-way switches.