Line Coding Flashcards
Why do line codes have to be added to synchronous systems ?
To maintain synchronicity and to help maintain a continuous signal
What do line codes specifically aim to do?
They aim to avoid long runs of 1’s and 0’s in the transmitted data stream
What are the simplest codes to implement ?
Non return to zero codes NRZ
What property do all non return to zero codes share?
The voltage level is constant during the bit interval, never returning to zero voltage, providing a constant data stream
What is a non return to zero level code ?
Absolute data, what is sent is received
What happens in differential decoding?
The signal is decided by comparing the polarity of the adjacent signal elements
Expand NRZL, NRZM, NRZS?
Non return to zero level,
Non return to zero mark,
Non return to zero space
Why are non return to zero codes implemented?
To break up long strings of 1’s is sent
What does a non return to zero mark code do ?
It changes the polarity every time a 1 is sent
A string of 1’s becomes a string of alternating 1’s and 0’s
What can non return to zero mark also be referred to as ?
Frequency differential keying - mark or delta 1
What does a non return to zero space do to the data stream ?
It changes polarity each time a zero is sent.
A sting of 0’s will become a string of alternating 0’s and 1’s
What is non return to zero space also known as?
Frequency differential keying - space or non return to zero inverted
What is another type of coding, other than non return to zero ?
Bi phase level coding
What is bi phase level coding also know as
Manchester coding or spilt phase coding
What does bi phase level coding do to the data ?
It inserts an extra bit so 2 bits represent one bit of original data
