telephone vs phone system

telephone and phone system both are nouns.

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

telephone (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
transmitting speech at a distance

telephone (verb)	phone system (verb)
get or try to get into communication (with someone) by telephone