Abstract: Each of a plurality of EL lamps in an instrument panel has its own control circuit for connecting the lamp to an adjustable AC voltage source. Each control circuit includes a photodetector for detecting the intensity of the illumination of its associated lamp, when the lamp is energized. With respect to a given input voltage of the AC voltage source, when the intensity of the light emitted by a given lamp begins to diminish, its control circuit will automatically increase the AC voltage applied across the electrodes of the lamp, thereby maintaining the light intensity of the lamp regardless of its age, for a given AC input voltage to the control circuit. The intensity of each lamp therefore remains consistent throughout substantially the full life of the EL lamp.