Front view of a Philips MLR 160W

Later self-ballasted mercury reflector fluorescent lamps produced by Philips were characterized by a clear front end which reveals the lamp's intricate inner construction. The assembly consists of a 90 V 51 W high-pressure mercury burner operating at 18 bars, connected to a 145 V 109 W ballasting filament. The power ratio between those two elements is chosen to ensure an optimal lamp operation considering that the mercury arc needs to re-ignite 100 times a second, after every zero current crossing. The latter aspect of the lamp operation is a rather difficult one given the resistive nature of the ballast, which resulted in a rather low mercury arc power level. A piece of hydrogen getter is also added to prevent the buildup of this light gas, which normally causes a gradual increase in re-ignition voltage over time.