B&O Two-Aspect Color Position Light Dwarf Signal
Motivated by impressive signals built by others, I decided to try my hand at some. A CPL popped into my head when I found a couple black Technic wheels in a bag I recently bought.
Color position light (CPL) signals used lights to mimic the arm of a semaphore, with each aspect having a different color. This one is capable of displaying stop (red) and restricting (lunar white) aspects. Prototype here.
It uses four Brickstuff lights, powered by one battery box. The wires run through the hollow cross section of my ballast profile to a yet unbuilt signal bungalow, which will also hide the battery box. The only downside right now is that plugs need to be switched to change aspects: Brickstuff doesn't make that kind of switch.