Editing Manchester code (section)

== Features ==
Manchester coding is a special case of [[binary phase-shift keying]] (BPSK), where the data controls the [[Phase (waves)|phase]] of a square wave [[Carrier signal|carrier]] whose frequency is the data rate. Manchester code ensures frequent line voltage transitions, directly proportional to the clock rate; this helps [[clock recovery]].

The [[DC component]] of the encoded signal is not dependent on the data and therefore carries no information. Therefore connections may be [[Inductive coupling|inductively]] or [[Capacitive coupling|capacitively]] coupled, allowing the signal to be conveyed conveniently by galvanically isolated media (e.g., Ethernet) using a [[network isolator]]—a simple one-to-one [[pulse transformer]] which cannot convey a DC component.

=== Limitations ===
Manchester coding's data rate is only half that of a non-coded signal, which limits its usefulness to systems where bandwidth is not an issue, such as a [[local area network (LAN)]].<ref name=":0">{{Cite web |last=Oed |first=Richard |date=2022-04-22 |title=Old, but Still Useful: The Manchester Code |url=https://www.digikey.com/en/blog/old-but-still-useful-the-manchester-code |url-status=live |archive-url=https://web.archive.org/web/20220822210500/https://www.digikey.com/en/blog/old-but-still-useful-the-manchester-code |archive-date=2022-08-22 |access-date=2023-02-02 |website=[[DigiKey]]}}</ref>

Manchester encoding introduces difficult frequency-related problems that make it unsuitable for use at higher data rates.<ref name=":0" /><ref>{{citation |url=http://docwiki.cisco.com/wiki/Ethernet_Technologies |title=Ethernet Technologies |publisher=[[Cisco Systems]] |access-date=2017-09-12 |quote=Manchester encoding introduces some difficult frequency-related problems that make it unsuitable for use at higher data rates. |archive-url=https://web.archive.org/web/20181228005303/http://docwiki.cisco.com/wiki/Ethernet_Technologies |archive-date=2018-12-28 |url-status=dead}}</ref><!--Difficulties are in meeting [[Title 47 CFR Part 15]] and other RF emissions requirements.-->

There are more complex codes, such as [[8B/10B encoding]], that use less [[bandwidth (signal processing)|bandwidth]] to achieve the same data rate but may be less tolerant of frequency errors and [[jitter]] in the transmitter and receiver reference clocks.{{citation needed|date=November 2015}}