Over the past year I have picked up all the parts to build a Lionel 78 signal. The only thing I'm missing now is an internal wiring diagram. The thing that has me truly perplexed is that I cannot see any connection between the wires from the track to the signal frame to complete the circuit for the bulbs. I'm assuming one of the wires from the outside rail somewhere connects to the frame but I cannot see where and the backing plate is made of a non conductive material. Where the 2 screw pass through the back plate there are no lugs. Any help, especially pictures, would be appreciated.
Thanks
Pete