[NextNewell]

I have seen considerable ($$$$$$) damage done to oil field generator sets when 2 were feeding into each other because manual isolation switches were not properly configured.  My advice is to take the time & effort to have it fixed right in the first place rather than having to take more time & $$$$$ to do it over.

I'm not saying that is what I'm doing, I'm just curious about what these actually do. I took one apart and it's simply two pieces that make contact when electrified. So other than it essentially being another on/off switch for electricity to pass through to the adjacent contactor coil, I don't see it doing anything else. And how they can go bad is another question altogether. 
But again, the switch inside only lets you choose shore, or generator, or neither, but never both. So if these only activate when the power is turned on at the switch above the driver and each contactor has a fuse to isolate them if stressed, then my simple mind asks, why the switch above the driver can't be connected directly to the corresponding contactor coil? 
Now I'm the first to admit I'm not schooled in electrical workings, but that's why I ask questions. 
I appreciate ALL the insight I am learning from this along with the very helpful advice from everyone on this forum: thank you.