cable television service vs cable system

cable television service and cable system both are nouns.

Word	Noun	Adjective	Verb	Adverb
cable television service	Yes	No	No	No
cable system	Yes	No	No	No

As nouns, cable television service and cable system are synonyms defined as:

cable television service and cable system: a television system that transmits over cables

Other synonyms of cable television service include cable, cable television.

cable television service (noun)	cable system (noun)
a television system that transmits over cables	a television system that transmits over cables