Non Return to Zero

From Computer History Wiki
Jump to: navigation, search

Non Return to Zero (usually given as the acronym, NRZ) is an encoding technique which is commonly used on magnetic storage and serial lines.

In NRZ, whether a particular bit is '0' or '1' is indicated by the signal level during each clock time; in other words, there is no 'rest' state between bits.

The disadvantage of NRZ is that a long strings of either value do not cause any level transitions (hence the name), so a separate clock is always needed, because it cannot be self-clocking (unless used with a periodic explicit clock, as in asynchronous serial lines; or with either bit stuffing or run-length limited coding, to limit the maximum number of transition-less bit times).

See also