Power Supply Unit
Power Supply Unit is an electronic machine that you can get voltage from, it used in the electronics lab.
You can get current AC/DC from it moreover there are three main outputs Negative, Positive and Ground.
The limit for DC voltage is 5 volt but in AC voltage you can get a higher voltage for example some Power Supply Units can give you between 230 V and 115 V.
There are two outputs for AC volt you can set they are parallel or series.

Reference
www.cs.wright.edu