... /MH electronic ballast.Welthink series digital electronic ballast can run HPS and MH bulbs both automatically under 100V~240V, ... the lamp, no need any external starter and compensation capacitor.Completely silent: no more humming and buzzing.Constant output ... resistance and maintenance free operationSoft startingDimming function is option.Approval: UL,CUL, EMC, ROSH,CE,TUV.Suitable Bulbs400W, 600W, ...