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Manchester code derives its name from its development at the [[University of Manchester]], where the coding was used for storing data on the magnetic drums of the [[Manchester Mark 1]] computer.
Manchester code was widely used for [[magnetic recording]] on 1600 bpi computer tapes before the introduction of 6250 bpi tapes which used the more efficient [[group-coded recording]].<ref>{{cite web |title=Digital Magnetic Tape Recording |author-first=John J. G. |author-last=Savard |date=2018 |orig-year=2006 |work=quadibloc |url=http://www.quadibloc.com/comp/tapeint.htm |access-date=2018-07-16 |url-status=dead |archive-url=https://web.archive.org/web/20180702234956/http://www.quadibloc.com/comp/tapeint.htm |archive-date=2018-07-02 }}</ref> Manchester code was used in early [[Ethernet physical layer]] standards and is still used in [[consumer IR]] protocols, [[RFID]] and [[near-field communication]]. It was and still is used for uploading commands to the [[Voyager spacecraft]].<ref>{{cite web |last1=Hughes |first1=Mark |title=Communicating Over Billions of Miles: Long Distance Communications in the Voyager Spacecraft |url=https://www.allaboutcircuits.com/news/voyager-mission-anniversary-celebration-long-distance-communications/ |website=All About Circuits |access-date=27 September 2024 |date=2 July 2017}}</ref>
== Features ==
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==Encoding and decoding==
[[Image:Manchester encoding both conventions.svg|class=skin-invert-image|thumb|650px|An example of Manchester encoding showing both [[Manchester code#Conventions for representation of data|conventions for representation of data]], where : {{math|1=''[[Leet|1337]]''<sub>10</sub> = ''10100111001''<sub>2</sub>}}]]
Manchester code always has a transition at the middle of each bit period and may (depending on the information to be transmitted) have a transition at the start of the period also. The direction of the mid-bit transition indicates the data. Transitions at the period boundaries do not carry information. They exist only to place the signal in the correct state to allow the mid-bit transition.
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Encoding conventions are as follows:
* Each bit is transmitted in a fixed time (the period).
* A <code>0</code> is expressed by a low-to-high transition, a <code>1</code> by high-to-low transition (according to G. E. Thomas's convention – in the IEEE 802.3 convention, the reverse is true).<ref name="Manchesterencoding">{{Cite journal |author-last1=Forster |author-first1=R. |title=Manchester encoding: Opposing definitions resolved |doi=10.1049/esej:20000609 |journal=Engineering Science & Education Journal |volume=9 |issue=6 |pages=278–280 |date=2000|doi-broken-date=12 July 2025 }}</ref>
* The transitions which signify <code>0</code> or <code>1</code> occur at the midpoint of a period.
* Transitions at the start of a period are overhead and don't signify data.
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[[Category:Line codes]]
[[Category:Department of Computer Science, University of Manchester]]
[[Category:History of computing in the United Kingdom]]
[[Category:History of telecommunications in the United Kingdom]]
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