When your train leaves the isolated loop, the mainline polarity has to be changed to match that of the isolated track your train is coming from. The wiring is illustrated in the following diagram... Model Train Wiring for Reverse Loop Track...
Refer to the Dimmer Switch diagram in Step 7. The Stop Light Switch doesn't care which wire goes where, just that they are FOR that purpose. Now we have a bundle that needs to find its way down the drivers side (inside) frame rail. Thread the rest of this portion of the harness ...
Case 1: power arrives in the electrical box where the switch will be mounted and runs through the switch and on to the light; the light has to have its neutral wire in its electrical box running back to the panel. Case 2: power arrives in the electrical box where the light fixture ...