Looking at the input terminal of the switching power supply, it says “L” and “N” instead of “AC”. What does that mean? If you haven’t been particularly concerned about it, please read below.
Outlet 「L」 and 「N」
There is no indication on the outlet of the house or office, but there are 「L」 and 「N」. It is confusing because there are many names, but the grounded side of the outlet is called N (Neutral or Cold, GND, Minus), and the non-grounded side is called L (Live or Hot, Plus). N means neutral, and Live means that the voltage is “alive”.
If you look closely at the outlet, the length of the hole in the outlet is different on the left and right. The hole on the left is 9mm long, the hole on the right is 7mm, and the hole on the left is a little longer by about 2mm.
The longer hole on the left side is N (ground side), and the shorter hole on the right side is L (non-ground side). Since the N terminal of the outlet has the same voltage as the ground, 0V and the L terminal are 100V (± 100V, but it is 100V for easy understanding).
In rare cases, the wiring on the back of the wall of the outlet may be mistakenly connected in reverse during electrical work, and the L and N of the outlet will be reversed. In that case, you cannot tell just by looking at the outlet from the outside.
To check if the outlet is wired correctly, you can check using a device called an “electroscope driver“. The voltage detection driver has a simple mechanism that the lamp lights up when a voltage is applied to the tip. It is sold at “Kohnan” and “CAINZ” for about 1000 yen, so if you are interested, why not buy it? It’s easy to use, just insert a voltage detection screwdriver into the hole of the outlet and press the button. If the wiring is correct, you can see that the L side on the right side is lit and voltage is applied. Even if you insert it into the hole on the left side and press the button, it will not shine because it is 0V. If it is wired in reverse, the left side will shine. Please do not do the wiring work of the outlet by yourself. Only qualified personnel can do it.