telephone set vs phone system

telephone set and phone system both are nouns.

Word	Noun	Adjective	Verb	Adverb
telephone set	Yes	No	No	No
phone system	Yes	No	No	No

telephone set (noun)	phone system (noun)
electronic equipment that converts sound into electrical signals that can be transmitted over distances and then converts received signals back into sounds	a communication system that transmits sound between distant points