Thanks for all the suggestions, I need to explain. Before DCC, when my layout ran on block control DC with four walk around plugged throttles, color coded, and separate dedicated throttles for my big yard, logging operation, seaport and engine operations like the round house and storage tracks, etc.,
Each throttle had a common ground but the output end was just a 1/4 inch phono plug (see picture) which now are not connected. The knotted grey wire has lugs that connect all blocks together for DCC, the flat head plug, second down on left which comes out of the yellow hole and is now plugged into Cab1 comes from the Digitrax output.
All it takes to convert any section, like the the yard, say, is to unplug the DCC plug (gray) and plug in a DC throttle, say white, and that section is now controlled by DC while the others stay DCC.
By unplugging the main DCC plug and connecting the DC throttle the whole layout is now controlled from that throttle since all blocks are connected by the gray knotted wires with plugs that could be disconnected by just pulling the plugs. The phono plugs are just a single wire even if it is a stereo plug, I just used what was at hand.
This system was put in because I put in a home brew computer block advance system that, when a route was selected to go from point A to point B, the computer would give the power to that cab one block ahead and drop the the power of the previous block as soon as the caboose was out of it and give that block to another cab if it was requested. It worked great and I didn't regret drilling 10,000 holes into 164 home etched PC boards and mounting the components.
Then I had a lightning strike that did a lot of damage to all electronics in the house and also wiped out the route program stored in an EPROM.
DCC had come along and I decided to go with DIGITRAX, a good decision, IMO.
Why I even brought up this discussion is that I wanted to have a rescue locomotive when a train gets stuck deep in one of my tunnels. The radio controlled loco can go in and nudge the train past the bad contact spot while DCC is still on the rails and it would resume it journey. For that to happen I wanted a locomotive independent of track power and with my battery controlled one now it is fine.
I have a three way slide switch on the locomotive that connects the power either from the battery or from the rail, but in order to run it from rail power DCC I need to rectify it into pure DC. So for rescue missions it would run on battery and for other train running it could use the rectified DC form the DCC rails.
I apologize for the length of the post but I wanted to clarify my situation, thanks for reading.
....Ott