Line code: Difference between revisions

Revision as of 15:16, 11 October 2004

Revision as of 20:20, 4 December 2004

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In [[telecommunication]], a '''line code''' is a [[code]] chosen for use within a [[communications system]] for [[transmission (telecommunications)|transmission]] purposes.

For digital data transport '''line coding''' is often used. Line coding consists of representing the [[digital signal]] to be transported, by an amplitude- and time-discrete signal, that is optimally tuned for the specific properties of the physical channel (and of the receiving equipment). AfterThe line[[waveform]] coding,pattern theof signalvoltage canor directlycurrent beused putto onrepresent the 1s and 0s of a transmissiondigital line,signal inon thea formtransmission oflink variationsis ofcalled the'''''line currentencoding'''''.

After line coding, the signal can directly be put on a transmission line, in the form of variations of the current. The common types of line encoding are [[Unipolar encoding|unipolar]], [[Polar encoding|polar]], [[Bipolar encoding|bipolar]] and [[Manchester encoding]].

A line coded signal must not contain a DC-component (the average signal level should be 0), because transport of a DC-component is impossible in case of long wires. An included DC-component would therefore lead to an offest at the receiving end, and thus to a higher decoding error probability.