An intermediate switch, known in North America as a four-way switch, is wired into the traveler lines between two standard multi-way switches. It functions by mechanically crossing over the connections between the two pairs of traveler wires. By adding multiple intermediate switches in series, a single lighting circuit can be toggled from an unlimited number of locations, such as at every door in a long hallway.
We need an intermediate switch at the middle landing so they can control the stairwell lights from all three floors.
When wiring these, the travelers from the first switch land on one pair of terminals, and the travelers heading to the next switch land on the other pair. Mixing them up breaks the entire switching logic.
Also heard as
- four-way switch
Related terms
Three-way switch
A single-pole, double-throw switch used in pairs to control a load from two locations.
Two-way switch
A standard switch controlling a load from one location, or a multi-way switch in UK terminology.
Traveler
One of the two conductors run between three-way switches, carrying power on whichever path is selected.