Return-to-zero
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Return-to-zero (RZ) describes a line code used in telecommunications signals in which the signal drops (returns) to zero between each pulse. This takes place even if a number of consecutive zeros or ones occur in the signal. This means that a separate clock does not need to be sent alongside the signal, but suffers from using twice the bandwidth (data-rate) as compared to NRZ format. The signal is self-clocking.
Although return-to-zero (RZ) contains a provision for synchronization, it still has a DC component resulting in “baseline wander” during long strings of 0 or 1 bits, just like the line code Non-return-to-zero.
A variant, Return-to-zero, inverted, swaps the signal values for one and zero.
An important variant is the Carrier Supressed Return-to-Zero (CS-RZ) used in optical communications.
