Signalling control

The raised design of most signal boxes (which gave rise to the term "tower" in North America) also provided the signalman with a good view of the railway under his control.

With the jump to all electronic logic, physical presence was no longer needed and the individual control points could be consolidated to increase system efficiency.

Another advancement made possible by the replacement of mechanical control by all-electric systems was that the signalman's user interface could be enhanced to further improve productivity.

Finally, the use of Automatic Route Setting removed the need for any human input at all as common train movements could be fully automated according to a schedule or other scripted logic.

Signal boxes also served as important communications hubs, connecting the disparate parts of a rail line and linking them together to allow the safe passage of trains.

Later, the telephone put centralized dispatchers in contact with distant signal boxes, and radio even allowed direct communication with the trains themselves.

The ultimate ability for data to be transmitted over long distances has proven the demise of most local control signal boxes.

Track circuits transmit train locations to distant control centers and data links allow direct manipulation of the points and signals.

This is especially true when signaling centers control large amounts of territory spanning many diverse lines and geographical regions.

In many countries, levers are painted according to their function, e.g. red for stop signals and black for points, and are usually numbered, from left to right, for identification.

In a signal box with a control panel, the levers are replaced by buttons or switches, usually appropriately positioned directly onto the track diagram.

Both in the UK and Ireland, however, mechanical signalling is still relatively common away from the busiest lines; in Europe, there is also a considerable amount in Germany, Poland, and the Czech Republic.