Line code

line codingbaseband transmissionencoding schemecodingEncodingencodedline coding schemeline encodingmodulation format
In telecommunication, a line code is a pattern of voltage, current, or photons used to represent digital data transmitted down a transmission line.wikipedia
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Unipolar encoding

Common line encodings are unipolar, polar, bipolar, and Manchester code.
Unipolar encoding is a line code.

Manchester code

Manchester encodingManchesterManchester coding
Common line encodings are unipolar, polar, bipolar, and Manchester code.
In telecommunication and data storage, Manchester code (also known as phase encoding, or PE) is a line code in which the encoding of each data bit is either low then high, or high then low, for equal time.


modulatedmodulatordigital modulation
By modulating the data, RLL reduces the timing uncertainty in decoding the stored data, which would lead to the possible erroneous insertion or removal of bits when reading the data back.
The aim of digital baseband modulation methods, also known as line coding, is to transfer a digital bit stream over a baseband channel, typically a non-filtered copper wire such as a serial bus or a wired local area network.

Pulse shaping

pulse-shapingpulse shaperpulse
Typically pulse shaping occurs after line coding and modulation.

Transmission (telecommunications)

In telecommunication, a line code is a pattern of voltage, current, or photons used to represent digital data transmitted down a transmission line.
Transmission technologies and schemes typically refer to physical layer protocol duties such as modulation, demodulation, line coding, equalization, error control, bit synchronization and multiplexing, but the term may also involve higher-layer protocol duties, for example, digitizing an analog signal, and data compression.


baseband signalbase bandcellular baseband
Digital baseband transmission, also known as line coding, aims at transferring a digital bit stream over baseband channel, typically an unfiltered wire, contrary to passband transmission, also known as carrier-modulated transmission.

Paired disparity code

paired-disparity code
In telecommunication, a paired disparity code is a line code in which at least one of the data characters is represented by two codewords of opposite disparity that are used in sequence so as to minimize the total disparity of a longer sequence of digits.


A scrambler can be placed just before a FEC coder, or it can be placed after the FEC, just before the modulation or line code.

Run-length limited

RLLrun length limitedMFM
For reliable clock recovery at the receiver, a run-length limitation may be imposed on the generated channel sequence, i.e., the maximum number of consecutive ones or zeros is bounded to a reasonable number.
Run-length limited or RLL coding is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits.


4B3T, which stands for 4 (four) Binary 3 (three) Ternary, is a line encoding scheme used for ISDN PRI interface.

Constant-weight code

M of n codes1 out of M codeConstant weight code
Most line codes use either a constant-weight code, or a nearly-constant-weight paired disparity code.

Differential coding

differential encodingDifferential
There are several different line codes designed to be polarity insensitive -- whether the data stream is inverted or not, the decoded data will always be correct.

Coded mark inversion

In telecommunication, coded mark inversion (CMI) is a non-return-to-zero (NRZ) line code.

DC bias

DC componentDC offsetDC
Most long-distance communication channels cannot reliably transport a DC component.
In order to avoid these kinds of bit errors, most line codes are designed to produce DC-balanced signals.

Bipolar encoding

Alternate Mark InversionAMIbipolar
Common line encodings are unipolar, polar, bipolar, and Manchester code.
In telecommunication, bipolar encoding is a type of return-to-zero (RZ) line code, where two nonzero values are used, so that the three values are +, −, and zero.


Two-binary, one-quaternary
Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL).

8b/10b encoding

8b/10b8B10Brunning disparity
In telecommunications, 8b/10b is a line code that maps 8-bit words to 10-bit symbols to achieve DC-balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery.

64b/66b encoding

In data networking and transmission, 64b/66b is a line code that transforms 64-bit data to 66-bit line code to provide enough state changes to allow reasonable clock recovery and alignment of the data stream at the receiver.

Modified AMI code

Alternate mark inversion (AMI) line codes are modified by deliberate insertion of bipolar violations.


In telecommunication, 4B5B is a form of data communications line code.

Eight-to-fourteen modulation

Early disk drives used very simple encoding schemes, such as RLL (0,1) FM code, followed by RLL (1,3) MFM code which were widely used in hard disk drives until the mid-1980s and are still used in digital optical discs such as CD, DVD, MD, Hi-MD and Blu-ray using EFM and EFMPLus codes.
Eight-to-fourteen modulation (EFM) is a data encoding technique – formally, a line code – used by compact discs (CD), laserdiscs (LD) and pre-Hi-MD MiniDiscs.


RZreturn to zeroRZI
Return-to-zero (RZ or RTZ) describes a line code used in telecommunications signals in which the signal drops (returns) to zero between each pulse.


NRZINRZnon-return-to-zero, inverted
Common line encodings are unipolar, polar, bipolar, and Manchester code.
In telecommunication, a non-return-to-zero (NRZ) line code is a binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negative voltage, with no other neutral or rest condition.

Differential Manchester encoding

biphase mark codeFMBi-Phase
Differential Manchester Encoding (DM) is a line code in which data and clock signals are combined to form a single 2-level self-synchronizing data stream.

MLT-3 encoding

MLT-3 encoding (Multi-Level Transmit) is a line code (a signaling method used in a telecommunication system for transmission purposes) that uses three voltage levels.