After doing some thinking ( not allways good in my case). I am asking how does this thing work? We are working with AC voltage here, so if we make a loop and connect the wires we make a short, OK I got that. Now we insulate the loop at both ends so we have a section (center) that is powered by the reverse detector. When we go across the gaps into the loop we could go in with the rails being powered up with out a short because the center section is the same polarity as the section we just left. Ok now we leave the center section and enter into the first section, now we have the center section and the first section that are no longer the same polarity. This is were the reverse detector must switch the polarity so we don't have a short. How does the reverse dector switch your main power, as this power is comming from your main buss? It seams to me there must be somthing in the DCC power supply or booster that would change the polarity. Or I would guess that when we make the short when we leave the center section and go into the first section the detector changes the center section so we now have the same polarity. The same would apply if we reverse the wires at the first section- now when we enter the center section, the dectector sees a short and switches the polarity so they match Any input-- Not to highjack TrainNut's post, but just trying to understand what is going on .