In reading about DCC and 'reversing loops' I am confused as to how and what is needed for a DCC loco to continue running when it meets track that is different polarity. I have a section of track that because of the way that the routes run the trains will be running in both directions. Do I need a special 'reverse loop' DCC module, or do the DCC units on the Loco's automatically recognize the difference in polarity and instantly make the switch on the locomotive for continuous running?
Without a graphic, not sure exactly what is going on here... but Digitrax explains how to handle DCC reversing loops here. I am currently rewiring my layout to trash all my old DC Block wiring and put in a simpler, better planned wiring plant of DCC. I ordered an AR1. They are pretty simple so you don't have to think about the polarity. Digitrax AR1 Link (PDF Format)
Any time that a DC layout would have the reversing loop problem - tracing a finger along one rail can come back to the starting point on the opposite rail - a DCC system needs an reversing mechanism. Be it a DPDT switch (from DC days), an Auto-reversing module, or one of the new Auto Reversing Boosters. The decoders themselves are not smart enough to solve the polarity problem, and worse, the short-circuit created by an engine crossing the block into the "reversed" section may be enough to fry the decoder.
I get the feeling that maybe you're confused about polarity and the need for reversing loops? In DCC simply because the trains are running in opposite directions does not mean that the polarities are reversed. DCC does not have polarity like DC does, as it's an AC signal on the tracks. If you have a loop of track the loops around and re-connects to the original (reversing the direction of travel of a train) then you need a auto-reversing loop mechanism. If you can operate the layout as a DC system (in one direction on the supply) throughout the entire layout without changing polarity on the tracks you have no reversing problems. In the layout I'm building I'll have no reversing loops, but plenty of possibilities for trains to simultaneous operate in different directions, mainly in the yard, but also in the local vs. main-line tracks. Mark in Utah
Overly simplistic explanation follows.... The DCC signal on the tracks alternates polarity about 8000 times per second. DCC commands are sent by slightly changing this frequency (sort of) in a pattern to represent the ones and zeros of the command. The decoder in the loco merely decodes these commands and routes one polarity or the other to the motor to control actual direction of movement, so two locos can be going different directions on the same track at the same time (hopefully not toward each other!) .
