phone system vs telephone exchange

phone system and telephone exchange both are nouns.

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

phone system (noun)	telephone exchange (noun)
a communication system that transmits sound between distant points	a workplace that serves as a telecommunications facility where lines from telephones can be connected together to permit communication