Signals in HO
HO Scale PC-board "sticks" to avoid using wires through a tube to the LEDs in the signal head. It makes it extremely easy to connect your electronics to it below the layout, no soldering or stripping of magnet wires to be connected to bigger wires, color coding (which wire is the green LED?)...simply pull the male pin header from the spring loaded holes in the PCB stick, and then you simply lift the signal up from above the layout. Free to work on or replace. The LEDs also solder to the PCB, so no need to struggle with alignment and more dangling wires. Simply rotate the LEDs do switch from a common-anode to common-cathode configuration. Resistors on the board, one for each LED, so no need to put that in your copper wiring either!
The first "production" run at a very famous railroad club! (Unfortunately now extinct!)