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How It works
What It is?
Telecommunication, devices and systems
that transmit electronic or optical signals
across long distances. such as a telephone
enables people to send and receive
personal messages .
key medium for delivering news, data,
information, and entertainment.
Way of sending Message
Point-to-point : One sender to a
single receiver such as telephone
Point-to multi point : one sender to
many receiver such as television, It
often called Broadcast;
How the signals sent?
Telecommunications devices convert
different types of information, such as
sound and video, into electronic or optical
Electronic signals travel along a medium
such as copper wire or are carried over the
air as radio waves. Optical signals travel
along optical fiber cable;
the device on the receiving end converts the
signal back into an understandable
message, such as words and pictures on a
computer screen.
Types of signal
Analog signal
Digital signal
Optical signal
analog or digital
refers to the
method used to
convert information
into an electrical
Analog signal
An analog signal is any continuously variable
in an analog sound recording, the variation in
pressure of a sound striking a microphone creates
a corresponding variation in the current passing
through it. An increase in the volume of the sound
causes the fluctuation of the current to increase
Digital signal
0 volt
means 0
5 volts
means 1
Optical signal
Pulse beam of laser
LED (Light Emitting
Diode) send signal
Fiber optic receiver
Receive fiber optic
Transmission medium
Coaxial cable
 Developed in 1936
 Made of copper wire
 Expensive
Fiber Optics
Message are digitally coded
into pulses of light
TAT 9 fiber optic cable can
carry more than 75,000
telephone conversation at a
Microwave relay
 Relay from station to station
 Needs a clear line of sight
between sending and
receiving station
 Average distance between
stations 40km
 As many as 600 telephone
conversations can be
transmitted over one
microwave relay channel.
Satellite communication
 Started at 1969
with series of
 Orbit 35,880km
above the earth
 Powered by solar
 Use micro wave
for transmission
 can relay up to
33,000 calls
as well as
several television
Way of transmission
 Simplex: One way
 Half Duplex:
communications in
both directions, but
only one direction at
a time
 Duplex:
communication in
both directions
Global Positioning System
Voice Over IP
Computer network
Telephone & cellular
Global Positioning System
 space-based radionavigation system
consisting of 24
satellites and
ground support.
 accurate
information about
their position, time,
anywhere in the
world and in all
weather conditions.
How GPS Works
 GPS satellites fly in circular orbits at an
altitude of 20,100 km (12,500 mi) and
with a period of 12 hours
 point their solar panels toward the sun
and their antennas toward the earth
 Send the signals to the receiver
 From that signal receiver calculate its
position on earth
Application of GPS
 Military equipment such as fighters, bombers,
tankers, helicopters, ships, submarines, tanks,
jeeps, and soldiers
 Airplane and ships use it for route navigation
 used to route and monitor delivery vans and
emergency vehicles
 car navigation system
 Because the GPS user does not need to
communicate with the satellite, GPS can serve
an unlimited number of users.
In 1837 Samuel
Morse invented the
first workable
 Alexander Graham
Bell invented
telephone in 1876
 Marconi invented
Radio in 1895