input signal vs signal

input signal and signal both are nouns.

Word	Noun	Adjective	Verb	Adverb
input signal	Yes	No	No	No
signal	Yes	Yes	Yes	No

As nouns, signal is a hypernym of input signal; that is, signal is a word with a broader meaning than input signal:

Other hypernyms of input signal include sign, signaling, signalling.

input signal (noun)	signal (noun)
signal going into an electronic system	any nonverbal action or gesture that encodes a message
	any incitement to action
	an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

input signal (adjective)	signal (adjective)
	notably out of the ordinary

input signal (verb)	signal (verb)
	communicate silently and non-verbally by signals or signs
	be a signal for or a symptom of