Line code
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In telecommunication, a line code is a code chosen for use within a communications system for transmission purposes.

Note 1: A line code may differ from the code generated at a user terminal, and thus may require translation.

Note 2: A line code may, for example, reflect a requirement of the transmission medium, e.g. , optical fiber versus shielded twisted pair.

Source: from Federal Standard 1037C and from MIL-STD-188

The original article can be found at: http://en.wikipedia.org/wiki/Line_code.
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