Victron Filax 2 Transfer Switch:
The Filax is an ultra-fast AC transfer switch. It ensures that a sensitive or critical load, such as computers or mission critical equipment, is always powered, either from the priority source or from an alternate source. The priority source typically is the mains, a generator or shore power.
If the priority source has failed, or is outside voltage or frequency specification, the Filax will transfer the load from the priority source to an alternate source. The transfer time is less than 16 milliseconds, so that the load is always powered and continues operation without disruption. Once the priority source has been restored and is within specification for at least 30 seconds, the Filax will transfer the load back from the alternate source to the priority source. The Filax is not intended to supply high power household equipment like washing machines or electric motors.
Data sheet here
Manual here
NOTE: This unit requires installation by a licensed Electrician.