This is a stabilized power supply unit using the IC NJM317 (or compatible) for variable power supply. The output voltage is DC 1.25 V ~ and can be adjusted from a maximum of 23 V (with input voltage of DC 25 V). Simple variable power supply in standard, but it comes with a circuit board for expanding functionality. When you install a commercially available voltmeter or switch, you can configure a professional laboratory power supply.