telly vs receiving system

telly and receiving system both are nouns.

Word	Noun	Adjective	Verb	Adverb
telly	Yes	No	No	No
receiving system	Yes	No	No	No

As nouns, receiving system is a hypernym of telly; that is, receiving system is a word with a broader meaning than telly:

telly: an electronic device that receives television signals and displays them on a screen
receiving system: set that receives radio or tv signals

Other hypernyms of telly include receiver.

telly (noun)	receiving system (noun)
an electronic device that receives television signals and displays them on a screen	set that receives radio or tv signals