Line coding consists of representing the digital signal to be transported, by a waveform that is optimally tuned for the specific properties of the physical channel (and of the receiving equipment).
The pattern of voltage, current or photons used to represent the digital data on a transmission link is called line encoding. The common types of line encoding are unipolar, polar, bipolar, and Manchester encoding.
Signal
Comments
NRZ–L
Non return to zero level. This is the standard positive logic signal format used in digital circuits.
1 forces a high level
0 forces a low level
NRZ–M
Non return to zero mark
1 forces a transition
0 does nothing
NRZ–S
Non return to zero space
1 does nothing
0 forces a transition
RZ
Return to zero
1 goes high for half the bit period
0 does nothing
Biphase–L
Manchester. Two consecutive bits of the same type force a transition at the beginning of a bit period.
1 forces a negative transition in the middle of the bit
0 forces a positive transition in the middle of the bit
Biphase–M
There is always a transition at the beginning of a bit period.
1 forces a transition in the middle of the bit
0 does nothing
Biphase–S
There is always a transition at the beginning of a bit period.
1 does nothing
0 forces a transition in the middle of the bit
Differential Manchester
There is always a transition in the middle of a bit period.
1 does nothing
0 forces a transition at the beginning of the bit
The conversion of the digital data into the digital signal is known as Line Coding. The data in digital is in the binary form. It is represented by the 1 and 0.
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