The NRZ-M bivalent coding method eliminates the disadvantages of NRZ coding, namely that DC voltage fluctuations occur with long 0 and 1 sequences on the transmission path and, in addition, synchronization
can no longer be established. NRZ-Mdigital signal
is 1. In NRZ-M, if the digital signal is 1, there is a transition from the previous state to the other. If the NRZ-M level was high before, it changes to low; if it was low before, it changes to high. If thedigital signal has a 0, then no level change takes place with NRZ-M coding.
With this coding, additional level changes are generated for synchronization with long 1 sequences.