Hughes telegraph vs telegraphy

Hughes telegraph and telegraphy both are nouns.

Word	Noun	Adjective	Verb	Adverb
Hughes telegraph	Yes	No	No	No
telegraphy	Yes	No	No	No

As nouns, telegraphy is a hypernym of Hughes telegraph; that is, telegraphy is a word with a broader meaning than Hughes telegraph:

Hughes telegraph: the first telegraph printing text on a paper tape, invented by David Edward Hughes.
telegraphy: apparatus used to communicate at a distance over a wire (usually in Morse code)

Other hypernyms of Hughes telegraph include telegraph.

Hughes telegraph (noun)	telegraphy (noun)
the first telegraph printing text on a paper tape, invented by David Edward Hughes.	apparatus used to communicate at a distance over a wire (usually in Morse code)
	communicating at a distance by electric transmission over wire