I am still a newbie and follow this group carefully. I have found the knowledge and information conveyed most helpful. A great learning tool to read responses such as those from Dave in Australia!
I have been monitoring the discussion about the importance of separating the programming track from the layout. I have a separate programming track, physically unconnected to the rest of the layout (a siding that disappears into a tunnel that goes nowhere). I have separate parallel power bus wires to the layout and to the programming track. To avoid the problem of programming locos on the layout when using the programming track, I could remove all the locos from the layout (not an attractive option) or use the described DPDT switch.
Am I correct in understanding that I only need to connect one of the two bus wires to the layout, and one of the two bus wires to the programming track respectively to opposite “sides” of the switch — one bus wire to the layout and one bus wire to the programming track, to each side of the DPDT. This should assure that only one of the separate parallel power bus circuits (to the layout or to programming track) is completed at any time. I’d probably use the same “polarity” wire (red or black) from each bus just to minimize chance of screwing up.
Do I have that right?