X-10 Pro XP4A-I X10 4 button keypad, Ivory, 3 X10 Keypads are used with the XPT TRANSMITTER BASE , sold separately. An X10 PRO VERSION "A" XPT TRANSMITTER BASE (Version "A" keypads will NOT work with older, NON-version "A" bases. The XPT is mounted into a standard single-gang wall box and is wired to HOT and Neutral. Using the XPT and keypad, you can set up 3 and 4 way light switching WITHOUT the need for "traveller wires" between the switches All Lights ON Commands cause only those Lamp and Wall Switch Modules typically associated with lighting to respond. (Note, Appliance and Outlet Modules do not respond to an All Lights ON Command but do respond to ALL OFF).