There are places where you want to be able to control a light --or a series of lights-- from more than one location. Three-way switches, classically used at each end of a stairway or hallway, are the answer --these are not new. Three-way dimmers will work at those same places. A standard three-way dimming control can be mounted at one end of the hall or stair, or you can buy special two-location dimming controls for dimming from either end. Four-way on/off switches may be combined with three-way dimmers or switches when you want control of lights from three or more different locations.
What is relatively new in this category is a variety of new devices that
allow you to operate many different light and equipment circuits from a
single location. With these, you can, for example, control all of the house
lights from the master bedroom. One typical model, the LiteTouch control
station is the same size as a normal light switch cover but operates nine
different light (or motor control) circuits. Multiple-station controls can
be preset for entertaining so that, with a single touch, they provide candle-like
atmosphere in the dining room, relaxed, tranquil lighting in the living
room and bright, activity lighting in the kitchen.
--Don Vandervort