MAIN88 By connecting one or more 4-way (intermediate) switches in-line, with 3-way switches at either end, the load can be controlled from three or more locations. Switching a load on or off from two locations (for instance, turning a light on or off from either end of a flight of stairs) requires two SPDT switches. Using the traveler system, there are four possible permutations of switch positions: two with the light on and two with the light off.|By using this Site