signaler vs signalman

signaler and signalman both are nouns.

Word	Noun	Adjective	Verb	Adverb
signaler	Yes	No	No	No
signalman	Yes	No	No	No

As nouns, signalman is a hyponym of signaler; that is, signalman is a word with a more specific, narrower meaning than signaler:

signaler: someone who communicates by signals
signalman: a railroad employee in charge of signals and point in a railroad yard

Other hyponyms of signaler include bell ringer, ringer, toller, whistler.

signaler (noun)	signalman (noun)
someone who communicates by signals	a railroad employee in charge of signals and point in a railroad yard