line coging

Line Coding: Design Consideration 3
Line Coding – process of converting binary data (sequence of
bits) to a digital signal
• digital signal depends ‘linearly’ on information bits - bits
are transmitted ‘one-by-one’ - different from block coding


Data vs. Signal Level
• data levels – number of values / levels used
to represent data (typically only two: 0 and 1)
• signal levels – number of values / levels allowed in a particular signal DC Two signal levels, two data levels. Three signal levels, two data level


DC Component
in Line Coding
– some line coding schemes have a residual (DC)
component, which is generally undesirable

 transformers do not allow passage of DC component
DC component ⇒ extra energy – useless!
Self-Synchronization
(Clocking)
– to correctly interpret signal received from
sender receiver’s bit interval must exactly
correspond to sender’s bit intervals
• if receiver clock is faster/slower, bit intervals
not matched ⇒ receiver misinterprets signal
• self-synchronizing digital signals include
timing information in itself, to indicate the
beginning & end of each pulse (see pp. 8-10)