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In telecommunication, a non-return-to-zero (NRZ) line code is a binary code in which "1s" are represented by one significant condition and "0s" are represented by another, with no neutral or rest condition, such as a zero amplitude in pulse amplitude modulation (PAM), zero phase shift in phase-shift keying (PSK), or mid-frequency in frequency-shift keying (FSK). The pulses have more energy than a RZ code, but it does not have a rest state, which means a synchronization signal must also be sent alongside the code.
NRZ is used in the RS-232 serial protocol. Internal computer signals often use this code.
Contrast with: return-to-zero.
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