Plugging into shore power.... Buzzing noise

falconman, I'm pretty sure that what tropical36 is referring to is......Many gassers (my previous as well) didn't even have a transfer switch. When you were plugged into shore power, the power (obviously) went into the coach electrical system. However, when you unplugged from shore power, you merely plugged the shore power cord into an outlet (typically located in the power bay) that was wired directly to the generator. You could then run the coach on generator power. (The generator became the source of power as opposed to the shore power pole.) It was a very simple but effective system. Much easier to maintain and no expensive transfer switch to deal with. Frankly, I sort of liked it.