4-way switch wiring diagram
Light: on
Toggle any of the three switches. The 4-way in the middle either runs the travellers straight through or crosses them — that is the whole trick. Tap a conductor to replay the current path. The copper highlight is the live path, not a wire colour.
A 4-way circuit controls one light from three or more places. It keeps the two 3-way switches at the ends and drops a 4-way (intermediate) switch between the travellers. The 4-way either passes the travellers straight through or crosses them, so throwing it flips the light like any other switch.
How this circuit works
Start with a plain 3-way: two switches, two travellers, light on when both ends agree on a traveller. Now cut the travellers in the middle and insert the 4-way. In its straight position it reconnects them as they were, so the circuit behaves exactly like the 3-way. In its crossed position it swaps the two travellers, which is the same as flipping one of the end switches.
That is the whole device: a pair of travellers in, a pair out, and a blade that chooses straight or crossed. Toggle the 4-way above and watch the copper path jump from one traveller to the other. Because every switch on the run either picks a traveller or swaps the pair, every switch changes whether the path completes — which is why any of them turns the light on or off.
Need six-way control? There is no such switch. You add another 4-way. Every additional location between the ends is one more intermediate switch on the travellers, and the rule above never changes.
Questions people ask
What does the 4-way switch actually do?
It sits between the two travellers and either passes them straight through or swaps them over. That is its only job. Because it can reverse the two travellers, throwing it changes which traveller is live at the far switch, which flips the light — exactly like the end switches do.
How do I control a light from four or five places?
Keep the two 3-way (SPDT) switches at the ends, and add one 4-way (intermediate) switch between the travellers for every extra location. Two ends plus three 4-ways gives you five switches on one light. The rule never changes: the ends pick a traveller, each 4-way passes or crosses.
Why does every switch still toggle the light?
Each switch either changes which traveller the end switches are using, or swaps the pair in the middle. Any of those changes flips whether the path is complete, so any switch flips the light regardless of the others.
What is the difference between a 3-way and a 4-way switch?
A 3-way (SPDT) has three terminals and always sits at an end of the run. A 4-way (intermediate) has four terminals and always sits in the middle, between travellers. You never use a 4-way on its own — it only makes sense between two 3-ways.
Related
- 3-way switch wiring diagram — start here; the 4-way is built on top of it.
- Glossary: traveller
- All wiring diagrams
Learn one thing a week
Now and then a new diagram, drill, or reference sheet goes up. Leave your email for a short heads-up when it does — no spam, no selling it on, one click to leave.