This is a simulation of ABS (Automatic Block Signaling).
An occupied block will be shown as a white line.
An unoccupied block will be shown as a grey line.
The first and last blocks are "unsignaled", and will be shown as unoccupied at all times.
"Aspect" is how a signal appears (e.g.: red, flashing, etc.).
"Indication" is the action that is expected/required by the train crew (e.g.: Stop, Approach, Medium, Clear, etc.).
Any block occupied by a train will be protected by various signal indications.
The first signal will display a red aspect. (Stop)
The second signal will display a yellow aspect. (Approach)
The third signal will display a flashing aspect. (Medium)
The fourth and all subsequent signals will display a green aspect. (Clear Block)
Signals that are lunar indicate that trains may proceed at "Restricted Speed".
U-signals (" ⊃ ") are displayed for Eastbound trains. A train moving from Left to Right will be controlled by these signals (which are on the right, as you approach them.)
Contra-wise, backwards U-signals (" ⊂ ") are displayed for Westbound trains.
U-signals that are followed by a dot (e.g., " ⊃. ") are constantly "on". They will always display some indication.
Round signals (" ⚈ ") are "fixed". They never change color, and are constantly on.
Signals are lit in groups called "Master Blocks". If any train is anywhere inside a Master Block, all signals for that Master Block will be lit.
Divisions between Master Blocks are shown with a "period" in the block label row (i.e., between 3 & 4 and 6 & 7).
Cyan text is default text.
The three trains are controlled by the green buttons.