Signalling and telecommunications. This specialized engineering division installs and maintains the wayside signals, track circuits, switch machines, and radio networks that keep trains separated. When a signal drops out or a switch fails to throw, S&T maintainers are dispatched to troubleshoot the relays and wiring.
Heard on the job
The home signal is dark, so we're stopped here waiting for the S&T guys to fix a blown relay.
Related terms
Signalling
The systems and equipment used to control train movements and ensure safe separation.
Interlocking
An arrangement of signals and switches interconnected to prevent conflicting train movements.
Track circuit
A low-voltage electrical circuit running through the rails to detect the presence of a train.