What is a three-way switch used for?

A three-way switch is specifically designed to control a single light or a group of lights from two different locations. This functionality is particularly useful in scenarios such as stairwells, long hallways, or large rooms where it is inconvenient to walk to one location to turn the light on or off.

When a three-way switch is installed, it allows any of the switches to control the light independently, which adds convenience and safety to the design of the lighting system. This capability is made possible through the unique wiring configuration of the three-way switch, which utilizes two traveler wires and a common terminal to create a circuit that can be completed in more than one way.

Other options do not pertain to the specific application of a three-way switch. A three-way switch does not serve to control lighting from a single location, connect multiple circuits, or transform AC to DC power, as these functions rely on different types of switches or devices designed for those particular uses. Therefore, the function of a three-way switch is accurately encapsulated in controlling a light from two different locations.