Intermatic RC939 Transmitter, Intermatic RC939, 3 ChannelModular Radio Receiver Controls With the push of a button on the face of the transmitter, the user is able to turn ON-OFF a receiver-connected load that is within 100 feet, inside or outside of the house. In addition, a single transmitter can operate up to three receivers and is able to "teach" each module a different code. (Receivers are sold separately) The receiver requires a neutral wire even if the switched load operates at 240v