Hi,
If the Pin&Flag switch is not ours then don't use it. Here is a link to the PowerExpander page, http://www.smart-fly.com/Products/Expander/expander.htm. Look at the picture UNDER the PowerExpander Pro picture. This is our Pin&Flag Failsafe Switch and Charge Package. You only need one to turn on/off both batteries and it plugs into the "Sw" input. Let me know if you have more questions.