Banjo Signal

This signal and others like it have 3 terminals. One for the red light, one for the green light and a common. It actually doesn't matter if the hot or the return is connected to the common as long as the opposite is connected to the others.

If both the green terminal and the red terminal are connected back to the transformer at the same time, they will both light up. What you need to do is alternate which terminal is connected to the transformer, green when the train isn't there and then red when the train is.

What confuses people is that they think they can use the outside rail for this directly, you can't because current only flows in the one case when the train is present. You need a relay of some sort that reacts to the presence or absence of current when the train is present and changes which terminal gets connected depending on whether or not the current is present.

I hope this is clear, I only recently figured it out myself. The old style contactor, being mechanical had the red and green wires attached to something of a mechanical switch. That's why a single device, the contactor, worked on the older style track and not with the newer roadbed type track.

The 140 banjo signal only has two terminals.

You can use an insulated track section with a fixed voltage source to power it.

For example, if the outside rails of your track are connection to the "U" common terminal of a ZW, the trains could run off the "A" terminal, and the signal could be powered from the "B" terminal.

Dang, I was thinking of the block and dwarf signals I have, that I figured out. Sorry 'bout that.