posted
This is about the minimum for this situation. I will leave it to someone more into signalling to explain it. GeoffM, maybe.
Geoff M Member # 153
posted
There are only four "signals" as such, but each signal has two or three lamps in order to show different aspects. An aspect is a certain light combination. Each combination has a specific meaning to the engineer. In this case, I believe they're all red meaning "stop". A top green allows maximum speed; a top yellow means the next signal is at red.
The outer two signals have an extra lamp in order to show the "go slow over the switch" indication, which the two centre tracks do not need.