landline vs telephone circuit

landline and telephone circuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
landline	Yes	No	No	No
telephone circuit	Yes	No	No	No

As nouns, telephone circuit is a hypernym of landline; that is, telephone circuit is a word with a broader meaning than landline:

Other hypernyms of landline include line, phone line, subscriber line, telephone line.

landline (noun)	telephone circuit (noun)
a telephone line that travels over terrestrial circuits	a telephone connection