In defence of Nihil: as a child of the 50's myself, it's not that old.
and the electricity supply varies around the world. UK = 3 phase 415v = 240v per phase.
trust me 240 + 240 = 415 when the phase angle is put in ( generation is a cycle? (not THAT type of cycle) 3 take off points = the phases, and the angle between them = 360/3 = 120) In the US of A the voltages are different, as are the values from practically every other country. Don't even ask about the frequency (Hz) me Electrical geek ?? for the last 30 !!!! years.