That is a good question.. And I will tell you why
There are two different types of automatic transfer switch (Plus one other method)
The one I have, it's "Resting" state is "Shore power" if the electronics that control it fail,, I get shore power. If the relays, also called Solenoids or contactors fail. Well,, That I'll cover down the page. But if the electronics fail , Shore power is the "Default option".
The other kind, the default option is "NOT CONNECTED" if the control electronics fail.. you are out of luck.
The third system is a manual transfer system (An outlet, matching your shore cord, somewhere on the RV, usually NEAR (or on) the generator, plug in to use generator.
Sometimes epically if you hot switch (Fire up the generator with shore power present and teh air conditioners running) the inductive "KICK" of those big blower and compressor motors will cause arcing o the relay contacts, this can weld them in one or the other position, Not good.
This is why you should shut off shore power for 2 minutes (minimum) Before starting generator (or otherwise kill all loads first, I trip my main circuit breakers)
Home is where I park it!