An electricity controller is provided which comprises a first power control means for controlling output power from power generator 4 to a first level during a first period of start-up time for feeding, a second power control means for controlling output power from power generator 4 to a second level lower than first level during a second period after the first period, and a third power control means for controlling output power from power generator 4 to a third level greater than the second level and lower than the first level during a third period after the second period. A discharge tube 2 is heated during the first period for supplying a large amount of electric power to discharge tube 2 to elevate the tube temperature and thereby uniformly disperse mercury vapor in discharge tube 2. Subsequently, while the device maintains the tube at a relatively high temperature during the second period for supplying a small amount of electric power to discharge tube, it can effectively reduce and restrict the release amount of infrared ray from discharge tube 2 in order to enable a remote controller 8 to control a display device immediately after the indication.