Thanks for all the help. I've finally figured it out....I think. When shore power is connected all DC (via the converter) and AC circuits are powered. When the shore power plug is connected to the socket in the external box, the generator can power all DC (via the converter) and AC outlets. The inverter powers one of the two duplex sockets which are located behind the kick panel below the stove. This one socket is only powered by the inverter.
Message to Outfitter: It would sure help if the user's manual, which I have, gave just a little detail on this critical subject.
Again, thanks very much for the prompt responses. I could have diddled around for weeks trying to find a transfer switch.