The SATCO T5 preheat fluorescent lamps make use of a magnetic ballast to preheat the tube for a few seconds, before high voltage is applied to strike the mercury arc. Preheating allows the current to flow through each electrode. No additional power is applied across the electrodes during operation.|The SATCO S1904 T5 preheat fluorescent lamp makes use of a magnetic ballast to preheat the tube for a few seconds, before high voltage is applied to strike the mercury arc. Preheating allows the current to flow through each electrode. No additional power is applied across the electrodes during operation.