# Zero-phase vs Linear-phase vs Nonlinear-phase System

I don't understand what is the difference between these. I'm trying to figure out how to classify this system's phase response:

Would someone please tell me what it is and how you can tell?

## 1 Answer

The phase seems to be either 0 or $\pi$, which correspond to real positive and real negative frequency responses respectively.

So this can be considered a real (zero phase) system.