The document provides an overview of telecommunication, defining it as communication at a distance via various technologies. It discusses the components of data communication, the evolution of telecom services, and the participants involved, including public telecom operators and users. Additionally, it outlines the types of communication channels and the differences between analog and digital data.

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Telecom Technologies
Chapter 1 – Introduction

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Introduction to Telecommunication
 The term telecommunication means communication at a
distance. The word data refers to information
presented in whatever form is agreed upon by the
parties creating and using the data. Data
communications are the exchange of data between two
devices via some form of transmission medium such
as a wire cable.
 Network is a system in which a number of
independent computers are linked together to share
data and peripherals, such as hard disks and
printers

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Why Telecom Study
• Communication over a distance is essential to
civilization and this communication is
increasingly provided by electronic means.
• In Order to transport large amount information
quickly, telcom services are extensively used
in business, in social life & for
entertainment.

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Who provides telecom service &
Who are the participants?
• Telecom service are provided by public Telecom
operators (Eg: Ethio telecom) through telecom
Networks.
• Telecom networks provides traffic by means of
transmission links connected by switching
system.
• Participants: Business of telecom involves many
participants.
– Public telecom operator(PTO)
– Providers of service that involve also the
equipment & component manufacturer (for both
h/w & s/w)
– Financial Investors (Government or private)
– Users, also called as subscribers or customers

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Development of Telecom
• Most of our activities depends on using
information like human speech, written &
printed document & computer data.
• Similarly information can be processed, stored
& transmitted by means of technology.
• For transporting these information over a long
distance, Telecommunication is used by
converting these information into electrical
signals.
• Electrical communications started with the
invention of telegraph by weatstone & Morse in
1837

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Contd…
• 1837- Invention of telegraph
• 1870- telephony, telex,facsimile
• (1876- 1878)Alexander Grahambel invented 1st
telephone exchange
• 1970- Radio phone
• 1990- Home banking, cardless calling, cell
phone, messaging
• 2000- pocket phone,voice recognition, digital
end to end services,satellite business services
etc.

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Components of data communication
1. Message: is the information (data) to be
communicated. Popular forms of information
include text, numbers, pictures, audio, and video.
2. Sender: is the device that sends the data message.
It can be a computer, workstation, telephone
handset, video camera, and so on.
3. Receiver: is the device that receives the
message. It can be a computer, workstation,
telephone handset, television, and so on.
4. Transmission medium: is the physical path by which
a message travels from sender to receiver. Some
examples of transmission media include twisted-
pair wire, coaxial cable, fibre optic cable, and

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Cont...
5.Protocol: is a set of rules that govern data
communications. It represents an agreement between the
communicating devices. Without a protocol, two devices
may be connected but not communicating, just as a
person speaking French cannot be understood by a
person who speaks only Japanese.

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Telecommunication channel
Serial vs. parallel communications
• In serial communications
– A single bit will be transferred at a time using
the communication channel
– Bits will be reassembled at the destination
– Mostly used by computer peripherals like printers.
• In parallel communications
– Multiple bits (eg. Eight bits) will be transferred
at a time
– Needs multiple (parallel) communication channels

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 In communication system
 source & destination of information are the
two key e/ts.
 There are many types of communication. For
example:
 Face to face communication / talking to others
 Remote communication / exchanging of voice
signals b/n two persons using a telephone.
 Communication b/n a workstation & a server
over public telephone network using tele-
conferencing system

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Cont...
 Communication channel
 Is a physical path for a signal transmission.
Ex. Telephone cables – wireless communication
provide a physical path for analog audio signals
Television channels – wireless communication broadcast
audio – visual data. Generally powers of communication
among computer – revolutionized the today’s
information age. It is the reason for the birth of
computer network.

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• To increase efficiency
and productive,
organizations developed
various information
sstems to support each
major activity and
responsibility.

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Cont...
• Two types(Data communication)
 Local communications – is one of the types
of data communication, transfer the data
over a short distance.
 Telecommunications – also other types of
data communication, transfer the data over
long/ far distance.

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Data Representation Techniques
 The type of data to be transmitted can be in the
form of text, audio, and video in the form of
electrical signal, radio, laser, or other radiated
energy source.
 Data can be analog or digital
 The term analog data refers to information that is
continuous; digital data refers to information that
has discrete states.
 Example analog clock (with second, minute and hour
hands) and digital clock

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Cont...

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Data flow (simplex, half-duplex, and
full-duplex comm

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Signal Encoding techniques
 Digital data:- information that has discrete states
 Analog Data:- information that is continuous
 Digital Signal:- can have only a limited number of
defined values.
– Although each value can be any number, it is
often as simple as 1 and 0.
 Analog signal:- has infinitely many levels of
intensity over a period of time.
– As the wave moves from value A to value B, it
passes through and includes an infinite number of
values along its path.

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Cont...

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DIGITAL DATA, ANALOG SIGNALS
• The most familiar use of this transformation is for
transmitting digital data through the public
telephone network.
• The telephone network was designed to receive,
switch, and transmit analog signals in the voice-
voice frequency range of about 300 to 3400 Hz.
• digital devices are attached to the network via a
modem (modulator-demodulator), which converts digital
data to analog signals, and vice versa

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