A Google search for ETA 1251 found the attached two PDF files. The schematic shows the availability of two
power inputs, L1 and L2 which are jumped together in the 1251 and would be supplied separately in the 1251-4 version.
Does not
address a second
line fuse or what happens if you
plug the L2 AC
cord into an
outlet with hot and
neutral reversed.... would probably let a lot of
smoke out. Definitely seek the advice of someone with electrical knowledge before attempting.