reverse loop wiring.. how tough?? - Model Railroader Magazine

It's pretty easy in DCC. You need to isolate the section that is going to cause the problem. If it is part of a separate power district, set the booster it is attached to as an Autoreversing booster.

If not, in Digitrax terminology, you would need either an AR1 or PM42. The AR1 is a single circuit autoreversing module, the PM42 allows a single booser to be divided into 4 power subdistricts, each with autoreversing capability. Wire one of these between the autoreversing section and the power feeds. The AR1 also works with non-Digitrax systems.

In a nutshell, when the locomotive hits the gap that creates the short, one of these gadgets detects it and reverses the polarity before it can cause a problem. That's why it needs to be isolated, since it wouldn't do much good for the booster to reverse power on both ends of the short (still be a short).

My only experience is Digitrax, but I suspect the other major manufacturers have similar items available.