X-10 Pro Three-Way Dimmer Switch Model XPDI3-IW;

What makes this switch unique is that in addition to dimming lights, the DIM/BRIGHT feature also lets you adjust the speed of ceiling fans and other motor-controlled devices in up to 16 steps. Now when the temperature in the room goes up (or down), you can adjust the speed of your ceiling fan from any X10 transmitter without getting up from your seat. The Inductive Wall Dimmer Switch is ready for three or four-way circuits. A 3-way circuit requires one Inductive Dimmer Switch and one slave switch. A 4-way circuit would require a total of two 2 slave switches. Simply add additional slave switches for 5, 6 or more way circuits. For single pole applications, just cap off the red traveler wire. Please note that you must use the PRO Series slave switches, existing 3 or 4 way mechanical switches will damage the dimmer.