My Stepson just had his electrician wire a connection for us at the pad he poured next to his shop. This experienced electrician knew all about RV and marine shore power wiring. He has handmade adapters for folks (30 AMP pole to 50 AMP power cord) that only power one leg of the 50 AMP side. This adapter will not let you run two ACs or use every outlet in the RV, sort of a built in safety when using 110 30 AMP supply. He also hand builds normal adapters that power both legs of the 50 AMP side from one 110v leg, like the one you would buy. He sent me this link that illustrates 110V 50 AMP and the 30 amp 110v RV receptacle wiring. I would think that if an RV park has 240/220V outlets that can receive an RV connector they should be extremely well marked and/or locked until the rare need for this connection arises! There are two 110V 'Branches" in an RV,
here is the link:
http://www.google.com/search?client=...1%3B1024%3B736