A twin-output ballast for Berson ultraviolet lamps, rated to run two lamps in the 80–125 W band. The ballast sets the current the lamp arc runs at, so a ballast drifting out of specification changes delivered UV-C output without necessarily failing outright — the plant keeps running and quietly under-doses. Match the ballast to the lamp wattage actually installed rather than to the reactor model, as several Berson reactors were built with more than one lamp rating.