This is a Shindengen voltage regulator circuit (VRC) designed for use in automotive and industrial applications. The ST04-27F1-5103 VRC is part of the Shindengen F1 series, a range of adjustable voltage regulators that provide voltage up to 27V at 25A. It features a built-in current limiting function which will automatically reduce the output voltage if the current draw exceeds the rated current. The adjustable output makes this part ideal for applications requiring variable voltage settings. Other features include reverse polarity protection, thermal protection, and over voltage shutdown.