sigˈnalling or (US) sigˈnaling noun

sigˈnally adverb

Notably

signal box noun

A railway signalman's cabin or an automatic or semi-automatic control point for the signals for all railway lines in a section

signal letters plural noun (nautical)

Four letters by which an individual ship may be identified

sigˈnalman noun

1. A person who transmits signals
2. A person who operates railway signals

signal peptide noun

A short N-terminal peptide sequence involved in the passage of a protein across a membrane (also signal sequence)

signal-to-noise ratio noun (acoustics)

The relationship, usu expressed in decibels, between the wanted signal and the unwanted background noise