I am new to MH's too..... just picked mine up 3 days ago......
I have the same switch, and unfortunately I've already had to use it.
As buchanan said, it ties the two systems together
In mine anyway, it's a momentary switch that activates a solenoid.
My house battery was dead. :'(
I had my hydrometer, multimeter, and even a battery load tester at the ready to do my PDI. Unfortunately they had the rig plugged in and waiting for me so the only thing I could do was measure the voltage..... well the electrolyte was full and clear, and the voltage was ok so the only thing I could do was to trust the dealer.
So it's been sitting for a little more than a day with what should have been a fully charged battery, with just a few minutes with the house lights on..... So I decided to put my charger on it to top it off..... wouldn't you know it. 9% charge, 11.xx volts according to my charger.
Anyway, to your question..... It didn't have enough to start the generator.....I pressed the Emergency Start Switch on the dash with the chassis engine running, and it served as a jumper cable to the house battery to start the generator!
My PDI tech had described the switch to me as for the opposite.... if the chassis battery is dead you can start the engine form the house battery. I am only assuming that he's correct and that it goes both ways..... it makes sense.....
Here is my parallel complementary question:
What disengages the solenoid to disconnect the two systems?
Is it a time based thing?
Is it not until the voltage comes up on the other side?