This might not be prototypical, but I designed a signal system for my double-turnout junction. 2 signals for entering, 2 for exiting, and 2 for staying in the loop, for each direction.
Only one light at a time stays green, while all others are red, controlled by Atlas momentary button control.
It also controls the 2 turnouts and their frogs.
I bench tested the system, and am about to assemble it all.
The direction and signals 2/3 switches, I’m actually going to build latching transistor switches instead of the mechanical ones.
I’m not an electronics expert, so I hope this, even if not perfectly clear, makes sense.
Cost: next to nothing!
Edit: On my computer it showed an older version of my drawing in this post, so I reuploaded it.