270 volts (+/- 135 volts line-to-ground) is very common in North America for repeaters and pair-gain devices like you mentioned, because no special current limiting is required when each line is under 140 volts. Above 140, a sort of "D.C. GFCI" is required that limits the current to 25 mA line-to-ground and 60 mA line-to-line.
I know you'll be pleased to know that those limits have been determined to be "...unlikely to cause organic damage or harmful physiological effects."
(I'm not gonna touch it -- let's get Mikey!)
