phone jack vs telephone jack

phone jack and telephone jack both are nouns.

Word	Noun	Adjective	Verb	Adverb
phone jack	Yes	No	No	No
telephone jack	Yes	No	No	No

As nouns, phone jack and telephone jack are synonyms defined as:

phone jack (noun)	telephone jack (noun)
a jack for plugging in a telephone	a jack for plugging in a telephone