Audio/Video Glossary - Nrz/nrziNon Return to Zero (NRZ) is a digital coding system used in RS-232 serial data links. This coding system is polarity sensitive. Non Return to Zero Inverse (NRZI) is a coding system which is insensitive to signal polarity. In this system, low signal levels mean no change in logical levels, and high signal levels represent a logic change from "0" to "1" or vice versa. The NRZI system is more immune to interference and is widely used in digital systems, like SDI*.