[nic547]

The complete system only controls the train insofar as it can apply the brakes (and probably cut the steam). What it can do depends on the lineside equipment. On newer routes it replaces the signals, keeps track of where the train is, where it has to stop and how fast it can go. It communicates with transponders mounted between the rails and depending on the route via GSM-R with a "Radio Block Center". It might communicate with older, uk-specific safety equipment. It contains a black box to monitor the driver and train. The screen is just a part (the so-called "Driver Machine Interface") of the whole system. And it needs to meet a high level of safety.