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Nonreturn to zero (NRZ) encoding uses two discrete voltage levels to represent a binary 1 and 0. It can be two positive voltage levels, as with unipolar NRZ, or two discrete negative levels. 8)
NRZ is an encoding of data that comes in sevaral variations .. It basically doesn't allows to sent data with the clock "ENCODED" at the same time.
Let me give you an example .. In a magnetic media recording.. a floppy or a hard drive .. you record the data and the clock at the same time .. .Otherwise it would be impossible to know how may ones or zeros you have ..in magnetic media the data recovered depends of the motor speed ..this one is never exact ...So the data recovered is also variable in lenght .. In order to know when a bit ends you have to recover a CLOCK ... NRZ .won't .allows this! The same applies to communication transmision ..
examples of this type of encoding are MFM & RLL in the magnetic media
The encoding is not very complicated .. !
Non-Return-to-Zero 'does what it says on the tin': the signal does not return to zero unless it has to. If a string of 1s is present, the signal stays at the level corresponding to a 1 for the whole diuration of the string of 1s. This means it is (by itself) *not* good for e.g. magnetic data recording because it is very difficult to recover the clock (which can only be done from transitions) unless the data itself is coded to force reasonably frequent 0-1 or 1-0 transitions. NRZ would commonly be used where there is another source of clock, or where the data is coded to make clock recovery easy. RS232 uses NRZ, and enables clock recovery by enforcing a 1-0 transition from idle at 1 to the start bit at 0, but then only has transitions when the data changes, until ending at 1 for the stop bit(s) within 7/8/9 bit periods (depending on 7/8 databits, and optional parity bit). The only guaranteed transition is the start bit, and UARTS typically use 16x over-sampling to get acfcurate sampling of the data bits based on the timing of the strat-bit transition, which works fine at RS232 data rates upto 115kbits/s.
By contrast Manchester encoding guarantees at least one transition on every bit (so clock recovery is very easy), and MFM encoding every 1/1.5/2 bits (so clock recovery isn;t too hard).
Please do NOT waste the resource of this forum with this silly questions!!!!
You can find the answer of this question in any comm. book..or you can do so by googling...
If you want to increase your post count you should be patient.... you can not incrase your post count by this stupid questions...
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