Originally Posted by
Musician
Actually, fault monitoring is simpler with the single toggle, because then both switches have to move at the same time, and if they don't, that must be a fault.
With separate switches, the pilot can move just one, so the system can't decide as quickly.
So for a FBW aircraft, it makes sense to design for electronic fault monitoring, even if that means the pilot can no longer feel the underlying switch go bad.
This is very standard in industrial safety. Unless both channels move simultaneously, you disregard the input. Sometimes raise a fault that needs to be manually cleared, other times just wait for the next time both switches actuate together.
If you want to take it further, you have two switches, each of which has two contacts that must operate together. That's common for e.g. presses, where you don't just want to verify that the button was pressed, but that the user actually is clear and wanted to press it. Door release on some trains, too.