Resistor on toggle switch?


Gang, I have an O scale two rail 2 8 2  that came to me with a motor controller DG 583 and sound decoder DSX steam. I am trying to program the decoders. I think I understand that I need to turn power off to one to program the other and vice versa. There is a toggle on the bottom of the tender which appears to turn off the motor decoder. It is a single throw double pole toggle. The black wire from the tender truck goes to the center terminal and then exits on one of the outer terminals making a on off connection. This black wire also goes to the sound decoder before the toggle. I think I understand that. The red wire from the locomotive pick up goes to the center terminal on the other side. Using a red wire, one outer terminal goes to the sound controller and also goes to a leg of a orange white black gold resistor which I believe is 39 ohms. The other leg of this resistor goes to the other outer terminal. So no matter what position the toggle is in,  power goes to the sound decoder. My question is what is this resistor for and do I need to somehow break the circuit to the sound decoder in order to program one or the other? Would this be accomplished most easily by installing another toggle switch? Is there a trick I am missing in programming via decoder Pro? I have tried to set the sound decoder to a short address and then go back and program the motor controller to the long address and then go back and change the sound decoder to the long address but this fails me. Thanks in advance, Bruce in Mount Airy Maryland


I don't know what the 39 ohm resistor would be for.  Just leave it for now.

Some decoders have a lock and unlock CV in CV 15 and CV 16.  Check the manuals of your decoders.  If you didn't get the manuals with your locomotives, check the manufacturers' websites for their old manuals.  This capability allows you to have multiple decoders in a loco such as yours.  But you initially have to set up the lock.  So no matter what, you will have to disconnect one wire to your sound decoder.  If you don't have the CV 15 and 16 lock capability in your decoders, adding another switch is a good option.  Since it is O-scale, that option may be open to you.

Allan Gartner
Wiring for DCC