A signalman is a person who operates signals, especially on a railway.
Signalmen are important for keeping trains safe and on time.
Examples:
The signalman waved the flag to stop the train.
The signalman changed the light to green.
The signalman works in a small building near the tracks.
The signalman wears a big hat and a uniform.
The signalman controls the trains with special signs.
The signalman is always watching the trains to keep them safe.