Line Coding

MANCHESTER

RZ

UNIPOLAR

• A good encoded digital signal
• must contain a provision for synchronization

• the transition at the middle of the bit is used for both synchronization and bit representation

• Unipolar encoding uses only one voltage level
• Unipolar encoding is so named because it uses only one polarity.
• Polarity is assigned to one of the two binary states, usually the 1.
• The other state, usually the 0, is represented by zero voltage.
• Has dc component.
• Lack of synchronization is an issue in unipolar encoding.

POLAR

DIFFERENTIAL MANCHESTER

NRZ-I

LINE CODING is the process of converting binary data, a sequence of bits, to a digital signal.

• the transition at the middle of the bit is used only for synchronization.
• The bit representation is defined by the inversion or noninversion at the beginning of the bit.
• A transition means binary 0, and no transition means binary 1.

• The signal is inverted if a 1 is encountered
• A 0 bit is represented by no change

NRZ-L

BIPOLAR

• The level of the signal is dependent upon the state of the bit
• Positive voltage usually means the bit is 0
• Negative voltage usually means the bit is 1

• In bipolar encoding, we use three levels: positive, zero, and negative Zero level in bipolar encoding is used to represent binary 0.
• The 1s are represented by alternating positive and negative voltages.
• AMI = Alternate Mark Inversion