Parallax Power Supply&nbsp; Parallax Power Components ATS503 Auto Transfer Switch 50 Amp 120/240 Volt With a flick of the generator switch, the ATS 503 line generator switch from Parallax transfers power smoothly between shoreline power and generator/secondary power source, regardless of line voltage conditions Engineered for superior reliability in 50 Amp Electronic circuit board design is proven in extensive cycle testing to withstand heat and torque Easy installation