and if you're "Off the Grid" you would need to have a different frequency then what ever is used locally.

I said "grid off". LOL again I ask, what is the frequency of a loose piece of wire? Let me go ahead and answer this for you this time: there is none. Which is why an inverter can't tell the difference between being off the grid, and being on the grid with no power. They're both "no frequency". Is any of this getting through to you?