Pulse code modulation (PCM) is used to transform an
analogue wave form into digital that is compatible with a digital communication
system, the following steps are taken.
Sampling- Digital signal transmission is done by having samples from
analog signals. Sampling
we obtain samples of an analogue signal within a certain time
period. The analogue signal
will sample at every sampling interval. According to the Nyquest theorem
sampling frequency should be equal or greater than to the maximum frequency of
the sound wave.
Quantization- Sampling
gives a series of pulses with varying amplitude. Then the receiver can not
identify the every finite value in the amplitude. So without sending the real sample we put the sample
signals amplitude in to the recognized
number of levels. We ought to approximate the amplitude of the
sample to the nearest quantization level. The heights between two levels are called a zone.
Encoding - Encoding
means converting quantized levels into binary formats to suit for digital
transmission. Encoding represent the sign,
segment number
and the sample
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