Detecting anything is signal processing.
And if I am wrong about this - all the better! It is exactly the right kind of wrongness we need to progress science.
I don't need to 'store' the infinite set of natural numbers - that would require infinite space (memory).
But I can describe the infinite set in a single line of Python. Nat = lambda x=0: Nat(x+1)
It's just a space-time tradeoff.