Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level in gas discharge lighting arrangements. Load side control is provided by a timed interval controlled impedance, serially coupled between the ballast and the lamp(s). A circulating inductor, coupled in parallel with the controlled impedance, provides a current path between the power source and the lamp(s) at least during that portion of the AC waveform where the controlled impedance is in a substantially non-conducting state.

Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level of a gas discharge lighting arrangement having four or more gas discharge lamps with multiple ballasts. Load side control of each ballast is provided by a timed interval controlled impedance, serially coupled between the particular ballast and its associated lamps. A circulating inductor, coupled in parallel with each controlled impedance, provides a current path between the power source and the lamps at least during that portion of the AC waveform when the controlled impedances are non-conducting. The invention is equally operable at both 120 volt and 277 volt AC levels without major component changes.