75 volt but w/ 1 of the bulbs out, I replaced them all w/ 12 volt. cleaned it up and away she went! it's true about the flasher operating on 12 volts! BE CAREFUL to those out there that may wish to run that flasher for any length of time. It is only a very small electronic flasher. Obviously in this unit, it was anloy designed to run at right around 1 amp each bulb with 4-80 watt bulbs at 75 volts. When you do the math, by replacing the bulbs w/ 12 volt-35 watt units, you are now drawing 3 amps each! #3 TIMES what that flasher is designed to handle. For now, and for display usage for short stints, it's fine but when I ran it for about 10 minutes, the ol' flasher was getting pretty warm. couple that w/ its age, obsolescence and a bit of corrosion, I guess what I'm saying is I wouldn't run it for too long. Now I know they made 12 volt versions of these and I have a customer that claims to have one on his father's wrecker, which he claims to still use, occasionally but I don't know if it utilizes the same flasher. I guess, If I guy was to put this thing into use or wish to run it longer, the safe bet would be to put some relays in there. When I had this apart, the wiring for the lamp heads, themselves, was amazingly tiny. Like 24 gauge. I guess, when you're only drawing 1 amp, what more do you need? The lamp holders are simple rubber tractor housings made by another local vendor, J.W. Speaker in Germantown, WI, so it's kinda neat how Prime, based in Oak Creek, WI utilized a local source for the guts for these! That, and the dome from North American out of Wheeling.IL... all local sources!