telegraphy vs telecom

telegraphy and telecom both are nouns.

Word	Noun	Adjective	Verb	Adverb
telegraphy	Yes	No	No	No
telecom	Yes	No	No	No

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

telegraphy: communicating at a distance by electric transmission over wire
telecom: (often plural) systems used in transmitting messages over a distance electronically

Other hypernyms of telegraphy include telecommunication.

telegraphy (noun)	telecom (noun)
apparatus used to communicate at a distance over a wire (usually in Morse code)	(often plural) systems used in transmitting messages over a distance electronically
communicating at a distance by electric transmission over wire