Return-to-zero
In the article we present below, we are going to delve into the fascinating world of Return-to-zero. We will explore its origins, its evolution over time and its relevance today. From its many facets to its impact on society, we will delve into each aspect to give you a complete and enriching vision. Whether Return-to-zero is a historical figure, a social phenomenon, or a current topic, this article will provide you with the information you need to understand his importance and influence on the world around us. So get ready to dive into this exciting topic and discover everything there is to know about Return-to-zero.
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Return-to-zero (RZ or RTZ) describes a line code used in telecommunications signals in which the signal drops (returns) to zero between pulses.[1] This takes place even if a number of consecutive 0s or 1s occur in the signal. The signal is self-clocking. This means that a separate clock does not need to be sent alongside the signal, but suffers from using twice the bandwidth to achieve the same data-rate as compared to non-return-to-zero format.
The "zero" between each bit is a 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). That "zero" condition is typically halfway between the significant condition representing a 1 bit and the other significant condition representing a 0 bit.
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.
Return-to-zero in optical communication
Return to zero, inverted
Return-to-zero, inverted (RZI) is a method of mapping for transmission. The two-level RZI signal has a pulse (shorter than a clock cycle) if the binary signal is 0, and no pulse if the binary signal is 1. It is used (with a pulse 3/16 of a bit long) by the IrDA serial infrared (SIR) physical layer specification. Required bandwidth for this kind of modulation is: BW = R(data rate).
Bipolar return-to-zero (bipolar RZ)
For bipolar return-to-zero (bipolar RZ), a binary one is encoded as +V volts, a binary zero is encoded as −V volts, and 0 volt is used to provide padding and separation between bits.
Bipolar return-to-zero encoding is used by the ARINC 429 bus.
See also
Other line codes that have 3 states:
References
- ^ "RZ vs NRZ: Demystifying Line Coding Techniques!". www.rfwireless-world.com. Retrieved 2025-10-07.
Further reading
- Savard, John J. G. (2018) . "Digital Magnetic Tape Recording". quadibloc. Archived from the original on 2018-07-02. Retrieved 2018-07-16.
Line coding (digital baseband transmission) | ||
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| Basic line codes | ||
| Extended line codes | ||
| Optical line codes | ||