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1.1Transmission essentially involves transporting of information from one place to another.
Explain why digital transmission cannot be achieved by merely following the Sampling

Sampling theorem involves in three processes i.e. Sampling such that fs < 2fm (fm is the
maximum frequency of the band limited signal), Media, by low-pass filtering the original
signal can be obtained. Here reproducing the samples through a transmission media
cannot be achieved. Hence a technique is used to resolve this. i.e. PCM.

1.2 Explain the basic process of Pulse Code modulation.

Sampling ---- Quantizing – Encoding – Transmission

1.3 In practice, non-linear quantizing is deployed as against linear quantizing, explain the
reasons behind. 256 levels are used for non-linear quantizing and there are 8 segments
each positive and negative sample. Explain the basic characteristics of non-linear
quantizing used for European system (the A-law signal compression of 13 linear

NLQ is used to provide a good S/N ratio for a wider span of signals. This is essential as
about 90% of the signals lie between +Vm/2 and –Vm/2.

The following shows the NLQ characteristics.

1.4 Each quantized level will be converted to binary before transporting the quantized level
(related to the sample) into the transmission media. Assuming a telephone will generate a
maximum of +3072 mV calculate the encoded format that will be sent in the transmission
media for the following sample values.
i. + 2210mV
ii. + 128mV
iii. – 14mV
iv. –416mV


i. +2210mV = 1 111 0110
ii. +128mV = 1 011 0100
iii. –14mV = 0 000 1000
iv. –416mV = 0 101 0000