Model Railway Forum

I've never understood why there are two programming options, main or program track. Obviously the controller has no idea what it is connected to so it must do something different according to what you tell it, but what?

The difference is ... Programming mode only allows a limited and reduced current to flow to the programming rails, thereby hopefully protecting a decoder that may not have been installed correctly.
Programming on the Main (POM) uses full track power (current) and is often able to overcome a decoder failing to be addressed cause. However, it really should never be used on a new installation or the 'first time' of programming.

Thank you Brian, makes perfect sense now.

Am I right in thinking that the program track programs any/all locos on the track, and programming on the main only programs the addressed loco regardless of other locos on the track?

If you know the address of the loco then entering that should only programme that loco when using POM.
If you do not know the address of a loco then either option should really still allow it to be programmed. But the danger doing this with POM is then all other locos on those POM rails will also become reprogrammed! A lot depends on the DCC being used as to how it allows POM to be used.
Is that what you are asking?

Remember if using PoM that accessory decoders are also listening for programming commands.

RAF96 wrote: ↑Mon Jan 18, 2021 2:31 pm Remember if using PoM that accessory decoders are also listening for programming commands.

Well unless I've misunderstood Brian's explaination above, you dont have to actually use the main track to PoM? As I understand it you can just use a spare piece of track (I've used one before that is set up for a rolling road but thats by and by) to program it either way. The only difference being is if it fails to work on "Programing Track" switch to PoM without moving the loco and try it again. That way no harm can come to any other locos on the main track or accessory decoders connected to it. Is this correct?

It may also be dependent on the controller.
The Prodigy has separate outputs for programming and main - I have a separate piece of track that can be switched between P or M as needed.
But I believe NCE has both modes but only one output so a way of isolating the main layout would be needed to ensure no mishaps. A simple DPDT switch does the job.

Steve M wrote: ↑Mon Jan 18, 2021 3:41 pm It may also be dependent on the controller.
The Prodigy has separate outputs for programming and main - I have a separate piece of track that can be switched between P or M as needed.
But I believe NCE has both modes but only one output so a way of isolating the main layout would be needed to ensure no mishaps. A simple DPDT switch does the job.

The program track set up for NCE requires two isolating fish plates and a double switch, but if you are using the Booster on the main track to run 6 locos you have to disconnect the booster and revert to the original NCE power supply and remove the "curly" wire and revert to the flat wire to the handset I have mine set up so I can use the prog track as a siding when not required for programming by having the main track supply on one side of the switch, I also have a buffer with red LED on the prog track to show when power is on.

Right thanks guys. I wasn't aware that some controllers had separate outputs. I have the PowerCab but not the booster. It's a couple of years since I did any programming but remember I just used a spare piece of track.