26 lines
1.3 KiB
Markdown
26 lines
1.3 KiB
Markdown
---
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title: "Coded mark inversion"
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chunk: 1/1
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source: "https://en.wikipedia.org/wiki/Coded_mark_inversion"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T11:31:48.778759+00:00"
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instance: "kb-cron"
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---
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In telecommunication, coded mark inversion (CMI) is a non-return-to-zero (NRZ) line code. It encodes zero bits as a half bit time of zero followed by a half bit time of one, and while one bits are encoded as a full bit time of a constant level. The level used for one bits alternates each time one is coded.
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This is vaguely reminiscent of, but quite different from, Miller encoding, which also uses half-bit and full-bit pulses, but additionally uses the half-one/half-zero combination and arranges them so that the signal always spends at least a full bit time at a particular level before transitioning again.
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CMI doubles the bitstream frequency, when compared to its simple NRZ equivalent, but allows easy and reliable clock recovery.
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== See also ==
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Manchester code
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== References ==
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ITU-T G.703 (11/2001), Annex A, A.3. Definition of CMI.
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US 4325053, Pierre Le Brozec; Francois Ferret & Pierre Doussoux, "Method and a circuit for decoding a C.M.I. encoded binary signal", issued 1982-04-13
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== External links ==
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Media related to Coded mark inversion at Wikimedia Commons |