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2.  Transmission Media.
 Characteristics of Transmission Media and its type.
 Limitations and advantages.
 Primary cause of signal loss.
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3.  Sending of data from one device to
another is called transmission of data.
 Medium used to transfer data is called
‘media’.
 Transmission of data from medium is
called transmission media.
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5.  Guided Media
◦ Coaxial cable
◦ Twisted pair cable
 Shielded Twisted Pair (STP)
 Unshielded Twisted Pair (UTP)
◦ Optical fiber
 Unguided Media
◦ Microwave
◦ Radio transmission
◦ Satellite
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6.  Guided media is the media in which the
data signals/information flows through
some bounded media such as wire, cables
etc.
 The media itself is very important in
determining the limitations of
transmission.
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 Coaxial cable consists the following layers in its construction
◦ The copper conductor
◦ Insulation of plastic foam
◦ Second conductor or shield of mesh tube or metallic foil
◦ Outer jacket of tough plastic
 Coaxial cable can be used over longer distances.

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 It is comparatively inexpensive
 Its installation is comparatively simple
 It must be grounded properly in a network connection

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 A twisted pair consists of two insulated copper wires
arranged in a regular spiral pattern
 The twisting tends to decrease the crosstalk
interference between the adjacent pairs in a cable
 Twisted pair may be used to transmit both analog and
digital transmission
 Twisted pair is limited in distance, bandwidth and
data rate

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Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP)
• Ordinary telephone wire
• Cheapest
• Easiest to install
• Metal braid or sheathing that
reduces the interference
• More expensive, harder to
handle (thick , heavy)

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 Fiber optic cable is known as most sophisticated
cables used in long distance network
communications
 It has inner core of glass that conducts light. This
inner core is surrounded by cladding
 Cladding is nothing but the layer of glass material that
reflects the light back in to the core
 Each fiber is then surrounded by plastic sheath
plastic jacket glass or plastic
cladding fiber core

12.  Use total internal reflection to transmit
light
 Can use several different light sources
; LED (Light Emitting Diode), ILD
(Injection Laser Diode).
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MEDIA ADVANTAGES DISADVANTAGES
COAXIAL CABLE • Inexpensive
• Easy to expand
• Widely used
• Single cable failure
can take down an
entire network
• Limited in distance
TWISTED PAIR • Easy installation
• Capable of high
speed for LAN
• Low cost
• More difficult
installation
FIBER OPTICS • Fast speed
• Can go long distance
• Very costly
• Hard to install
• Bending is not easy

14.  Send communications signals through air
or space.
 Used when inconvenient or impossible to
install cables.
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15.  Earth-based reflective dish that contains antenna,
transceivers, and other equipment necessary for
microwave communications
 Uses line-of-sight transmission
◦ Must transmit in straight line with no
obstructions between microwave antennas
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16.  Microwave transmission covers a substantial portion
of the electromagnetic spectrum.
 Common frequencies used for transmission are in the
range 1 to 40 GHz.
 The higher the frequency used, the higher the
potential bandwidth and therefore the higher the
potential data rate.
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17.  Form of broadcast radio used widely for
mobile communications.
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• Some use
radio
frequencies to
connect the
workstations
together,
some use
infrared
technology.

18.  The range 30 MHz to 1 GHz is an effective one
for broadcast communications.
 A prime source of impairment for broadcast
radio waves is multipath interference.
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19.  Satellites are transponders (units that receive
on one frequency and retransmit on another)
that are set in geostationary orbits directly over
the equator. These geostationary orbits are
36,000 km from the Earth’s surface
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20.  Optimum frequency range for satellite
communication is 1 to 10 GHz.
 The most important property is the long
communication delay for the round trip (about 270
ms) because of the long distance (about 72,000 km)
the signal has to travel between two earth stations.
 This poses a number of problems, which are to be
tackled for successful and reliable communication.
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MEDIUM ADVANTAGES DISADVANTAGES
MICROWAVE • Point-to-Point
communication in
line-of-sight.
• Can be done quickly
at lower cost.
• Must have visual
contact between the
antennas
SATELLITES • Can be at high,
medium, or low orbit
used in GPS
• Expensive to build
and maintain
RADI O
TRANSMISSIONS
• Inexpensive and easy
to install
• Effective for short
ranges , used in
LANs
• Limited range ,
• difficult to secure

22.  Free space loss is the primary source of signal loss in
satellites.
 As the signal propagates through the atmosphere it
disperses with normal terrestrial antennas, the
distance is so short that is rarely an issue.
 However the great distance that satellites must
communicate over make this a major problem for
global space-based communication.

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