An improved luminaire load control system for handling control signals as by converting them into power line carrier communication signals which are transmitted through branch power lines to terminal control units without causing any significant interference to power line installation. the conversion of the control signals is done respectively at a plurality of gate way units mounted on each branch power line and each gate way unit further includes memory unit for storing the information regarding to the connecting status of the terminal unit for sending back the stored information to a central control unit upon receipt of a send back command therefrom. In a specific embodiment of the invention, a plurality of gate way units are mutually connected with specific signal transmission lines for providing the reciprocity control of luminaire loads by installing a plurality of operation command input terminals in each of the branch power line, whereby the control signal is transmitted through the specific signal transmission lines.