"RoyB"......great diagram as to how 50 amp systems work and how the dogbone adapter works.
"LinDens"....Here's something we do....We often camp at State and County parks with only 30 amps. We have the cheater box described above that allows you to plug into either two 30amp circuits or one 30 amp and one 20 amp circuit. This only works at a few campgrounds.
The better solution was that I wired an extra outlet into my bathroom and living room on a separate circuit from the coach. The wiring runs out to a 20' extension cord that is connected/stored in my power bay. Almost every campground where I have stayed with 30 amps always has a 30 amp and 15/20 amp outlet. I plug in the 15/20 amp cord in and use the outlets that I added for a space heater in the living room and blow dryer in the bathroom (not at the same time). This frees up power for other things in the coach, since my DP has some large power demands. (I didn't add a separate circuit breaker since the outlet at the pedestal is protected).
Others also wire their rear A/C to a switched second cord for hot weather.