One wire comes in from the power source, and one wire goes out to the light(s). A 3-way switch adds two terminals for travelers, which connect two 3-way switches together.

Diagram 1: Here's an example of a basic three-way switch layout, the type you'll hopefully deal with in your home. Steve Conaway/CNET If your lighting setup doesn't jive with these two pictures, I ...

One way to think about it is that your far-end switch has two input lines (the travelers) and one output line (the common), which returns to the fan or light fixture. One of the travelers is ...

There are two types of light switches, says Donnelly: a single-pole light switch, which has two wires, and a three-way light switch with three wires that usually look identical.

You can add a second light switch anywhere in your house without wiring a new three-way switch thanks to smart home technology. This guide will show you what you need, and how to do this without ...

That's where 3-way switches come in.. Unlike single-pole switches, which control lights from one location, 3-ways work in pairs. You must have two of them — and only two.