NRZ

In telecommunication, a non-return-to-zero (NRZ) 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 amplitude modulation (AM), zero phase shift in phase-shift keying (PSK), or mid-frequency in frequency-shift keying (FSK). NRZ is used in the RS-232 serial protocol.

For a given data signaling rate, i.e., bit rate, the NRZ code requires only half the bandwidth required by the Manchester code.

Contrast with: return-to-zero.

Source: from Federal Standard 1037C in support of MIL-STD-188.