Recent innovations in mine safety include the use of mercury vapor lamps for mine vehicle illumination. Such lamps, however, extinguish whenever the line voltage at the machine momentarily sags or is interrupted. The lamps must then cool for several minutes before they will restart. By supplying reduced high-frequency power to the lamps from an auxiliary source, it is possible to maintain ionization in the arc tubes preventing the lamps from extinguishing. Essentially an auxiliary high-frequency supply, the keep alive system provides additional power to the lamps automatically whenever the lamps are in danger of dropping out. With this system, the lamps can be dimmed for periods up to 3 minutes by interrupting the 60-hz power to the conventional ballasts. Each unit, housed in a steel explosion-proof enclosure with a volume of approximately 0.6 Ft3, is capable of servicing up to six 175-watt h-39 mercury lamps and two 100-watt h-75 reflector flood lamps.