Crossing Wiring

The information having to do with frog and crossover polarity reversal is irrelevant to Peco InsulFrog crossings. The information about track connecting to the crossing with the correct polarity is applicable all crossings, no matter how it’s made or who makes it.

A crossing has two frogs. How the polarity comes into the crossing will determine whether the frog or the rest of the crossing needs to flip polarity. Regardless, in most cases it’s easy to do — especially with DCC.

As you can see in Iillustration 1, there are two wires coming from the bottom side of the crossing; one from each frog. The wires are imbedded in groves in the ties.

If you’re running DCC you can use a Digitrax Auto Reverser or one output of a Digitrax PM42. That’s what the rest of this dialog will address. If using DC analog control, you’ll have to handle it in the traditional way — with toggle switches.

The first of four situations is where the polarity comes into both ends of the crossing with opposite polarities to the frogs, as shown in Illustration 2 at right.

Notice the rails that connect to the crossing’s stock rails are of the same polarity. But the rails that connect to the frog rails (blue) are two different polarity. This is the easiest situation to handle. Simply connect one frog to one output of the auto-reverser, and the other frog to the other output of the auto-reverser. Be sure to use insulated rail joiners on all four frog rails. You can use metal rail joiners on the stock rails.

The next situation, shown in Illustration 3, is where the polarity comes into both ends of the stock rails with opposite polarities. In this case, the stock rails become the reverse section. Connect the frogs with metal rail joiners, connect the stock rails with insulated rail joiners, connect one output of the auto-reverser to one stock rail (blue), and the other output of the auto-reverser to the other stock rail (blue).

The third situation, shown in Illustration 4, is more complex. It involves coming into one end of the crossing with like frog rails and the other end with like stock rails. That’s because you have a reverse section somewhere on the layout that hasn’t been taken care of.

Since there are two blue (reverse) sections, one might quickly think that all that needs to be done is to connect each one to an auto-reverser. But notice when traveling the yellow route that the polarity changes from one side of the crossing to the other. While the frog rail could change to red without any problem, the stock rail can’t be red and green at the same time. Even if it could, when a loco spans the crossing from one connecting track to the other, it would cause a short circuit.

In this particular situation you need to take care of the reverse section needs elsewhere to make the track polarity come into the crossing to match one of the previous two examples. Taking care of the reverse section on the lower left track would create a situation like in Illustration 2 — preferable. Taking care of the reverse section on the upper right track would create a situation like in Illustration 3 — not preferable, but easily handleable.

The fourth situation, shown in Illustration 5, is similar to the last one, in that there are reverse sections elsewhere on the layout that haven’t been taken care of.

Notice that the difference between this and the last situation is that no matter which route you take, the polarity reverses on the other side. This means that more than likely you have two reverse sections to fix elsewhere on the layout. To make handling the crossover polarities as easy as possible, it’s best to take care of both reverse section needs from the same end of the crossover. Doing this will make the stock rail polarities the same, and leave only the frogs to make reversible (with insulated rail joiners).

Again, polarity reversal is not applicable to Peco InsulFrog crossings, only to live frog crossings.