Editing Line code (section)

{{short description|Pattern used within a communications system to represent digital data}}

{{stack|
[[File:NRZcode.png|class=skin-invert-image|thumb|An example of coding a binary signal using rectangular [[pulse-amplitude modulation]] with polar [[non-return-to-zero]] code]]
[[File:Ami encoding.svg|class=skin-invert-image|thumb|An example of [[bipolar encoding]], or AMI.]]
[[File:Manchester code.svg|class=skin-invert-image|thumb|Encoding of 11011000100 in [[Manchester encoding]] ]]
[[File:Differential_manchester_encoding_Workaround.svg|class=skin-invert-image|thumb|An example of [[differential Manchester encoding]]]]
[[File:Biphase Mark Code.svg|class=skin-invert-image|thumb|An example of [[biphase mark code]] ]]
[[File:MLT3encoding.svg|class=skin-invert-image|thumb|An example of [[MLT-3 encoding]]]]
}}
{{Modulation techniques}}

In [[telecommunications]], a '''line code''' is a pattern of voltage, current, or photons used to represent digital data [[transmission (telecommunications)|transmitted]] down a [[communication channel]] or written to a [[storage medium]]. This repertoire of signals is usually called a '''constrained code''' in data storage systems.<ref>{{Cite journal 
|journal= IEEE Communications Magazine
|date=2022
|title=Innovation in Constrained Codes
|author=K. Schouhamer Immink
|author-link=Kees Schouhamer Immink 
|url=https://www.researchgate.net/publication/362866105
|access-date=2022-10-05
}}</ref> 
Some signals are more prone to error than others as the physics of the communication channel or storage medium constrains the repertoire of signals that can be used reliably.<ref name="optics">{{Cite journal 
|journal= IEEE Journal on Selected Areas in Communications
|volume=19
|date=2001
|title=A Survey of Codes for Optical Disk Recording
|author=K. Schouhamer Immink
|author-link=Kees Schouhamer Immink 
|url=https://www.researchgate.net/publication/3234561
|pages=751–764
|access-date=2018-02-05
}}</ref>

Common line encodings are [[Unipolar encoding|unipolar]], [[Polar encoding|polar]], [[Bipolar encoding|bipolar]], and [[Manchester code]].