Ok,Im thinking Bert is correct. I was infact able to power on at 120v. I'm curious now if I can power it up at 208 (ie the line to neutral voltage in a 240Y system) kind of odd to have a part number implying 120 operation, but a label implying 240v operation.I think ill call the company and ask for more info. Note: after peaking under the hood,this variac has no additional taps.The name plate is obvious,Simple diagram, 3 screw lugs.1 wired to the beginning of the coil2 is the wiper3 is wired at about 75% of the coil1 and 3 are connected to the strange little transformer cores, which arnt paralleling chokes (no interconnection to the other cores) I'll update again with any useful info I may find. -JaySent from my Verizon, Samsung Galaxy smartphone