Wiring diagram for a 3-way switch, one of the many wiring diagrams showing different methods of wiring a three way switch circuit. This electrical wiring diagram shows power into light switch Box #1 – wire to light from switch box #1, and from switch box #1 to three-way light switch box #2.
Note that in this case, a larger than normal device box is required at switch #1 location, due to box fill calculations (most regular size boxes will only accommodate five wires; in this situation, you will have seven wires).
NOTE: This is a thumbnail diagram. Click on it to enlarge it.
Need help understanding how a light switch (both single-pole and 3-way) works? Watch this great video that shows how they work!