diaphone vs foghorn

diaphone and foghorn both are nouns.

Word	Noun	Adjective	Verb	Adverb
diaphone	Yes	No	No	No
foghorn	Yes	No	No	No

As nouns, foghorn is a hypernym of diaphone; that is, foghorn is a word with a broader meaning than diaphone:

diaphone: a foghorn that makes a signal consisting of two tones
foghorn: a warning device consisting of a horn that generates a loud low tone

diaphone (noun)	foghorn (noun)
a foghorn that makes a signal consisting of two tones	a warning device consisting of a horn that generates a loud low tone
	a loud low warning signal that can be heard by fogbound ships