central vs phone system

central and phone system both are nouns.

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

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

central (adjective)	phone system (adjective)
in or near a center or constituting a center; the inner area
serving as an essential component