These are actually two modules, each built in two pieces to allow expansion. The modules feature DCC auto-reverse units to handle the polarity problem you get when building a reverse loop. In the photo, they're connected directly together but that's because we wanted to test them after finishing the wiring. They worked flawlessly the first time! :-)
We have operated the loops semi-successfully at one show in March but had problems with the auto-reverse units picking up moisture due to the hot-and-cold cycle of going from the house, to the car, to the show; the result was that they did not work.
Since that time, the auto-reverse units have been dried out and are working flawlessly once again. However, for extra insurance, we've added a bypass switch underneath to "remove" the auto-reverse units and also a DPDT toggle switch on top to handle manual polarity switching. In a test last Saturday, we had no auto-reversing problems.