Non Return to Zero Inverted

What Does Non Return to Zero Inverted Mean?

Non Return to Zero Inverted (NRZI) is a data recording and transmission method that ensures clock synchronization.


Techopedia Explains Non Return to Zero Inverted

Non Return to Zero (NRZ) is a binary code used in telecommunications transmission, where a data bit of 1 is positive voltage, and a data bit of 0 is negative voltage. NRZ code does not have a neutral state, versus Return to Zero (RZ) code, which has a rest state.

In the absence of independent clock signals, certain mechanisms are required when NRZ data is asynchronously coded. NRZI maps binary signals to physical signals during transmission. If a data bit is 1, NRZI transitions at the clock boundary. If a data bit is 0, there is no transition. NRZI may have long series of 0s or 1s, resulting in clock recovery difficulties.

An additional encoding mechanism must be used to ensure clock recovery. Run-length limited (RLL) encoding, such as that used with magnetic disk storage devices, is preferred over Universal Serial Bus (USB) bit stuffing, which often results in variable data transfer rates (DTR).


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Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…