you DO NOT want to have a generator online but no way to synchronize when the utility power comes on.
Allow me to relate a little story which happened at a British telecommunications facility some years ago.
In replacing the control modules for the generator set, somebody somehow managed to miswire the synchronizing circuitry and clearly didn't check it before putting it in service.
When they came to parallel two generators, the sync circuitry did it's job in matching speed and locking the gensets together. Unfortunately, they were synchronized out
-of-phase when the connection was made.
I understand they were retrieving engine parts out of the roof for some time......