this is PCM application

1. Topic PCM:
 Group Member:
 Haris Khan 159
 Usman Masood 131
 Umer Farooq 170
P.C.M. 1

2. P.C.M. 2
Pulse Code Modulation
Pulse Code Modulation (PCM) Is a Digital Scheme for
Transmitting Analog Data. The Signals in PCM Are Binary;
That Is, There Are Only Two Possible States, Represented
by Logic 1 (High) and Logic 0 (Low). This Is True No
Matter How Complex the Analog Waveform Happens to
Be. Using PCM, It Is Possible to Digitize All Forms of
Analog Data, Including Full-motion Video, Voices, Music,
Telemetry, and Virtual Reality (VR).

3. P.C.M. 3
Why PCM
The stream of pulses and non-pulse streams of 1’s and 0’s are
not easily affected by interference and noise. Even in the
presence of noise, the presence or absence of a pulse can be
easily determined. Since PCM is digital, a more general reason
would be that digital signals are easy to process by cheap
standard techniques. This makes it easier to implement
complicated communication systems such as telephone
networks.

4. P.C.M. 4
Introduction
PCM was invented by P. M. Rainey of
Western Electric in 1926 and later
improved by British engineer Alec
Reeves in 1937 while working for
International Telephone and
Telegraph in France. He filed for a
French patent in 1938, and his U.S.
patent was granted in 1943.

5. P.C.M. 5
Nomenclature
The word pulse in the term pulse-code modulation is somewhat
confusing, as there appear to be no "pulses" per se anywhere
to be found except in the transmission line. This perhaps is a
natural consequence of this technique having evolved
alongside two analog methods, pulse width modulation and
pulse position modulation, in which the information to be
encoded is in fact represented by discrete signal pulses of
varying width or position, respectively. In this respect, PCM
bears no resemblance to these other forms of signal encoding,
except that the binary numbers of the PCM codes are
represented as electrical pulses. The device that performs the
coding and decoding function in a telephone circuit is called a
codec.

6. P.C.M. 6
Implementation
 The practical implementation of PCM
makes use of other processes. The
processes are carried out in the order in
which they appear below:
 Sampling
 Quantizing
 Encoding

7. P.C.M. 7
Topics of Discussion
To obtain PCM from an analog waveform at the
source (transmitter end) of a communications
circuit, the analog signal amplitude is sampled
(measured) at regular time intervals. The
sampling rate, or number of samples per
second, is several times the maximum
frequency of the analog waveform in cycles per
second or hertz.

8. P.C.M. 8
Topic One-Sampling
 Details about this topic
 Supporting information and examples
 How it relates to your audience

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Topic Two-Quantization
The instantaneous amplitude of the analog signal at each
sampling is rounded off to the nearest of several specific,
predetermined levels. This process is called Quantization.

10. P.C.M. 10
Topic Three-Encoding
The number of levels is always a power of 2 -- for
example, 8, 16, 32, or 64. These numbers can
be represented by three, four, five, or six binary
digits (bits) respectively. The output of a pulse
code modulator is thus a series of binary
numbers, each represented by some power of 2
bits.

11. P.C.M. 11
Application
 Supporting information and examples-Digital information
is better transmitted in its digital form because converting
the signal to analog and sending it through an analog
network can be costly. Digital data is easily compressed;
therefore it can be transmitted using a small bandwidth.
Because of the nature of devices used to boost the signal
strength during transmission, error performance is much
improved when compared with analog. It is also better to
transmit information in digital form because computer
components used in the transmission process are very
reliable.

12. P.C.M. 12
Real Life
 The microphone and line-in circuits on a sound
card generate PCM samples, and all sound
cards require PCM for output. Compressed
audio formats such as MP3 and AAC are
converted to PCM first, and The sound card
converts the PCM to analog for the speakers.

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LIMITATIONS
It may be noted that there are two sources of
impairment implicit in any PCM system:
 choosing a discrete value near the analog signal
for each sample (Quantization error)
 between samples no measurement of the signal
is made; due to the sampling theorem this
results in any frequency above (fs
being the
sampling frequency) being distorted or lost
completely.

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END
Thank you