Wiring a 6 pin On/Off/On toggle switch (DC) 2 Pole
Figure 1. The common on one pole of the switch is connected to the upper or lower tag depending on switch position. The other pole of the switch is the same and is electrically isolated from the first.


Connect the monitor + and - to the common tags.
Connect one power source to the top tags, observing polarity.
Connect the other power source to the bottom tags, observing polarity.




Figure 2. Cross-section of a switch that was a serious problem on Apollo 15 due to a piece of wire floating around inside the switch. Source: Apollo 15
Day 2: Checking the SPS.

Don't buy stuff that doesn't have datasheets.