Explains what data communication is, modes of communications, cables can be used, guided and unguided media............etc

1. Chapter 3
Data communication
Prepared by: Anne Perera

2. What is data communication?
Transmission of data from one place to another
place is called data communication.
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3. Basic parts of data communication
Three components are essential in data
communication.
1. Sender / Source
2. Data Communication Medium
3. Receiver / Sink
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4. Basic parts of data communication
Sender/Source Receiver/Sink
Medium
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5. Sender / Source
Sender or source is the data producer or the
place where the data is produced for data
transmission.
E.g.: Imagine you call a friend of yours.
Then you become the Sender or Source.
Sender Prepared by: Anne Perera

6. Data Communication Medium
The medium which is used to transmit data to
the receiver.
E.g.: In the example mentioned above, telephone
becomes the data communication medium there.
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7. Receiver / Sink
The receiver is the person who gets data at the
end.
E.g.: Your friend is the receiver in the above
mentioned example.
Receiver
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8. Data Communication
Media/Medium
•Various media are used for data communication.
•It is possible to divide all these media into two
main types.
1) Guided Media
2)Radiated Media
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9. Guided Media
A particular physical medium is used for data
communication.
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10. Radiated Media
Communicating data using media which is not
physical, is called radiated media.
Eg: Radio transmission, Infrared, Microwaves
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11. Guided Media
Following wires can be classified under
guided media.
•Twisted wire pair (Twisted pair cables)
•Co-axial Cable / Coaxial cables
•Fiber optic cables
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12. Twisted wire pair
•The normal wires used for daily activities can also
be used for data communication.
•A twisted pair consists of two copper wires about
1 mm thick.
•Pairs of insulated copper wires twisted around one
another for the reduction of Electromagnetic
Interference.
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13. Types of twisted wire pair
1) Shielded Twisted Pair
2) Unshielded Twisted Pair
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14. Shielded Twisted Pair
A Shielded Twisted Pair (STP) has a fine wire mesh
surrounding the wires to protect the transmission.
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15. Unshielded Twisted Pair
•An Unshielded Twisted Pair (UTP) do not have a
wire mesh.
•Not suitable for long distance transmission.
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16. Twisted wire pair
Advantage of STP over UTP
STP reduces the interference.
Disadvantages of STP
It is more expensive than UTP.
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17. Advantages of Twisted pair cable
• Can carry both analog and digital data.
• Easy to implement and terminate.
• It is the least expensive media of transmission
for short distances.
• If portion of a twisted pair cable is damaged it
does not affect the entire network.
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18. Disadvantages of Twisted pair cable
• Very poor security and is relatively easy to tap.
• Thin in size, they are likely to break easily.
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19. Applications of Twisted Pair Cables
•Telephone lines to carry voice and data channels.
•ADSL lines.
•Some Local area networks.
•ISDN (Integrated Services Digital Network).
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20. What is ISDN?
Multiple devices can be attached to the line, and
used as needed.
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21. Asymmetric digital subscriber
line (ADSL)
•A type of digital subscriber line (DSL)
technology.
•A data communication technology that enables
faster data transmission over copper telephone
lines.
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22. Co-axial Cable / Coaxial cable
It has a copper net woven around a copper wire.
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23. Applications of Coaxial cables
•Used in digital transmission
•Used for analogue transmission
•Used for TV antennas and Cable TV
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24. Advantages of Coaxial cables
•Easy to install
•Not expensive
•Since it shielded, can span a higher distance at
higher speed than twisted pair.
•Less data loss
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25. Disadvantages of Coaxial cables
•Higher cost compared to twisted pair
•Cables easily get damaged
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26. Fiber Optics
•Avery popular guided media used today for data
communication.
•Fiber optics (optical fibers) are long, thin strands
of very pure glass about the diameter of a human
hair.
•They are arranged in bundles called optical
cables and used to transmit light signals over long
distances.
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27. Fiber Optics
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28. Applications of Fiber Optics
•Military -They offer better performance and
greater security for their signals.
They're strong, and lightweight, and can also be
used outdoors in harsh environments.
•Radar systems
•Telecommunications companies to transmit
telephone signals
•Internet communication
•Cable television signals
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29. Advantages of Fiber Optics
•Carry signals with much less energy loss than
copper cables.
•Much lighter and thinner than copper cables.
•Difficult to tap information.
•Supports for long distances.
•Supports for very high speed network
communications.
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30. Disadvantages of Fiber Optics
•It's very expensive.
•Difficult to splice two cables together
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31. Radiated Media (Unguided Media)
•No physical medium is used here to send data.
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32. Radiated Media (Unguided Media)
1. Radio transmission
Radio transmission, which is very familiar to our
normal lives, can be used for data communication
very easily.
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33. Radiated Media (Unguided Media)
2. Infrared
•It has a very low frequency.
•These are largely used for data communication
when wire- less keyboards, mouse and printers
are used.
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34. Radiated Media (Unguided Media)
3. Microwaves
•Used to communicate data to a long distance and
short signals with contain higher frequency.
•Microwave links use very high frequency
radio waves to transmit data through space.
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35. Microwaves
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36. Radiated Media (Unguided Media)
4. Communication satellites
Data can be communicated using satellites which
are installed high in the sky.
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37. Communication satellites
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38. Data Transmission Types
Data transmission can be done in two ways.
1.Serial data transmission
2. Parallel data transmission
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39. Serial data transmission
•Data is transmitted here, one after the other
(one bit at a time, in a serial way).
•Such data transmission is done in bits in a
computer network.
•One wire is enough here for data transmission.
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40. Serial data transmission
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41. Parallel data transmission
•Several bits are transmitted at a time
•Several wires are used for this.
•In most of the instances, use of at least eight wires
for this is the normal way.
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42. Parallel data transmission
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43. Data Transmission Speed
The speed of data transmission is measured in
Bits per second (bps)
Kbps (kilobits per second)
Mbps (Megabits per second)
Gbps (Gigabits per second).
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44. Data Transmission Modes
Three main modes are
1.Simplex
2. Half-Duplex
3. Duplex
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45. Simplex
•Data is directed one way only.
•There is no any space for data transmission to be
directed the other way.
Examples: Television transmission
Radio transmission.
From your computer to the printer.
From the mouse to your computer.
•Data transmission is always done here only from
sender to receiver.
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46. Simplex-Examples
One way only
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47. Simplex-Examples
One way only
Television transmissionPrepared by: Anne Perera

48. Simplex-Examples
One way only
Radio transmission
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49. Half-Duplex
Data can be directed one way at a time.
The data flows in one direction or the other,
but not both at the same time.
Example: Walkie-talkie.
Where only one party can talk to the other at a
time
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50. Half Duplex -Examples
Walkie-talkiePrepared by: Anne Perera

51. Half Duplex -Examples
Walkie-talkie.
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52. Duplex/Full duplex
Data can be transmitted both ways at a time.
Example: Telephone.
Both ways at a time
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53. Duplex/Full duplex
Router
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54. END
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