If you’ve done any electrical work, you probably have no trouble figuring out how to wire a fixture to a single switch (called a two-way switch), whether the source comes through the switch or the fixture. Basically, the switch interrupts the current.
But what if you want to have one light fixture operated by two different switches, as you normally would for a stairway light?
Now, a two-switch setup like this is called a 3-way switch. Believe it or not, it does make sense, since you’ll need a special switch with 3 terminals instead of two. Rather than interrupting the current, the switch redirects the current from one terminal to another (or from one wire to another).
Because you have two potentially “hot” wires running from the switch, you need to run 3-wire cable from the switch. This cable contains the two hot wires (black and red), a neutral wire (white), and the bare copper ground.
In a nutshell, the current goes from the first switch to the second switch, and passes from there to the fixture when the switches are aligned.
Hang on to this article. Next time, we’ll diagram the setup.