Don't know if this is what you want, but it's copied from a PECO booklet by Cyril Freezer on wiring the layout.
The following text applies as well:
The wiring gives automatic siding isolation. The frog rails are one electrical unit and are connected to the point blades so that the frog is at the same polarity as the the stock rail against which the the blades are held. this not only ensures that the open track has rails of opposing polarity but also means that the closed track has rails of the same polarity.
HTH
Doug
