On a rail transport

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

 system, signalling control is the process by which control is exercised over train movements by way of railway signal

Railway signal

A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts accordingly...

s and block systems to ensure that trains operate safely, over the correct route and to the proper timetable

Public transport timetable

A public transport timetable is a representation of public transport information to assist a passenger with planning a trip using public transport. A timetable details when vehicle will arrive and depart specified locations and may be organised for by route or for a particular stop...

. Signalling control was originally exercised via a decentralised network of control points that were known by a variety of names including signal box (British), interlocking tower (North America), signal poste (France) and signal cabin.