This might be trivial, but sometimes may drive those without much hardware experience crazy 🙂

The wiring method for a DC switching power supply is as follows:

AC input: 110V or 220V, sometimes controlled by a switch
“N” — Null Line;
“L” — Live Line;
“Earth”—Earth Line.

DC output:
“-V” — Negative Output;
“+V” — Positive Output.

Example of a DC switching power supply (S-15-5, Mean Well)