Q: What is a programming track?
A: A programming track is a section of track that is used to program the mobile decoders in locomotives. Sometimes it is called the service mode track or service mode programming track.
It must be electrically isolated from the rest of your layout and connected to the Prog A and Prog B terminals of your command station. The programming track can be completely separate from the rest of the layout or can be isolated by double gapping and using an electrical switch to allow locos to move from the programming track to the mainline before and after programming.
Usually only one locomotive is on this track at a time since when you are programming, you are changing the address of the locomotive, its performance and other operating characteristics.