A 50 amp RV outlet is wired exactly the same as a 50 amp residential range outlet, with two opposing phase hot legs, a neutral leg, and a safety ground. Properly wired, a volt meter will read ~240v from hot to hot, and ~120v from each hot to the neutral. Each leg can carry up to a 50 amp load. It's actually harder to miswire the 50 amp RV outlet than it is the 30 amp RV outlet that must be connected to a single 120v breaker. The 50 amp 120/240v confusion comes in because there are very few RV's that actual use 240v, but the wiring is exactly the same as standard residential 120/240v systems.