signalman

The word "signalman" is most strongly linked with railways. It originally meant the person responsible for operating signals, and often points (track switches), so that trains could travel safely along the line. A signalman usually worked from a signal box or another trackside post, watching the railway, communicating with other railway workers, and making sure trains were stopped, slowed, or allowed to pass at the proper time. In the days before modern automation, this was a vital job, and a small error could cause a serious accident.

The word can also be used in other settings for a man whose duty is to send, receive, or deal with signals, especially in military or naval use. In that wider sense, a signalman may handle flags, lamps, radios, or coded messages. Even so, the railway sense remains the clearest and most common meaning for many readers, especially in historical writing.

So the heart of the word is not just "someone who communicates" in a broad way. It points more specifically to a worker whose job is to control or pass on signals as part of transport or military operations. In modern use, the railway role is often historical because many systems are now automated, but the word still carries the image of a careful, watchful person whose signals help others move safely.