This Philips HF-Ri TD 1 28/35/49/54 TL5 dimmable ballast runs between : 1 x 28w, 35w, 49w or 54w T5 fluorescent tubes or 2 x 58w T8 lamps. This ballast\'s lamp power can be regulated from 1% to 100%, digital control input according to the industry standard DALI (digital addressable lighting interface) combined with the touch and dim pushbutton protocol, automatic stop start, automatic restart after lamp replacement, up to 75% reduction in energy consumption and quick programme flicker free start.The Philips HD-f ballasts are commonly used in offices. These units are for use with installations with emergency back up.