Universal automatic electronic phase switch PEF-301. Switch is designed to supply industrial and household appliance single-phase 220V/50Hz loads from three-phase four-wire mains 3x380+N with the purpose of maintaning uninterrupted power supply of essential single-phase loads and protect them against unallowable voltage variations in the mains.Depending on the voltage presence and voltage quality on phases, the PEF-301 will automatically select t..