The 208 that you refer to is the "high-leg" voltage to ground on a 240/120 volt 3 phase delta connected transformer secondary with on of the windings tapped at midpoint to provide 120 volts. The voltage of one of the phases, usually the "B" phase is about 208 and obviously should be avoided if connecting 120 volt equipment. There is also a wye connected 208/120 3 phase system where all 3 phases are at 120 volts to ground.
