Wiring a switch to a new power supply for a 12v lamp
The switch has 2 poles - Meaning it's basically two switches in one package.
Pins marked &quot;1/2&quot; is the first switch, and the pins marked &quot;4/5&quot; is the second switch.
It had 4 wires because the original setup would cut both the AC Hot &amp; Neutral lines.
For safety, it's really only necessary to cut the hot, but you never know if the wall outlet is wired right, so the even safer option is to use a switch that cuts both.  Hence 4 wires instead of 2.
In your repair, you can cut either the AC input or the DC 12V.   The difference is, if you cut the DC, the power supply will always be running and consuming a trickle of energy.