The document discusses various concepts related to communication systems including protocols, handshaking, error detection, transmission methods, network topologies, and hardware. It provides examples of different communication systems like email, teleconferencing, and electronic commerce. Issues with communication systems such as knowledge sharing, messaging, internet trading and censorship are also examined.

1. HSC Communication
System
2017 HSC Prep

2. Every communication system has 5 basic requirements
•Data Source (where the data originates)
•Transmitter (device used to transmit data)
•Transmission Medium (cables or non cable)
•Receiver (device used to receive data)
•Destination (where the data will be placed)
Characteristics of Communication
Systems

4. The necessity of protocols in
communication – a protocol is
needed when one computer
communicates with another where
one of its tasks is to ensure that
the data send by the sending
device is the same as the data
received by the receiving device.
A protocol is a set of rules that control a
communications link.

5. A protocol defines the format and
meaning of information exchanged by
describing parameters such as
▪speed of transmission (bps, baud)
▪transmission mode (answer or
originate),
▪handshake,
▪parity,
▪error detection and
▪correction.

6. The elements that a protocol controls
include: the type of language used
(e.g. ASCII), type of error checking
method used (e.g. checksum), what
to do when error is detected (e.g.
resend data), way data are sent
(asynchronous or synchronous
transmission) and how often
receiving computer needs to
acknowledge that it has received the
data.

7. Handshaking – is the exchange of
signals between two devices to
establish a communication link for
senders and receivers. The computer
handshakes to a printer or a modem in
order to establish a connection for
communicating. For a link between the
computer and modem, handshaking
involves the signalling of both to each
other that they are switched on and
ready for work………

8. …… The computer sends a DTR
(Data Terminal Ready) signal to
modem through a particular wire
used only for this signal. When the
modem is ready it sends a DSR
(Data Set Ready) signal to
computer through a different wire in
the connecting cable.

9. ▪Measuring speed in a
communication link : -
▪Baud rate – the number of
distinct signal events or timing
intervals in a second. If a
device like a modem can only
send on-off signals then its
bps equals its baud rate.

10. ▪ Measuring speed in a communication link : -
▪ Bits per second (bps) – the number of bits
that are transmitted in a second. This
measures the speed of communication. Bps
is the number of 0s and 1s which are
transmitted through the communication link in
one second.
▪ This includes special bits described in the
protocol, including start and stop bits and
various error checking bits. Bps is more
useful than baud rate as it shows how much
data is sent and how fast it is sent.

11. ▪Methods to check for errors in
communications links including: -
▪Parity bit check – this is a
character error detection
method. It adds an extra bit
to every character or byte
transmitted.

12. ▪Methods to check for errors in
communications links including: -
▪Check sum – adds together
the values of all the bytes
transmitted in a message
block and sends the total as
the last data byte of the block.

13. ▪Methods to check for errors in
communications links including: -
▪ Cyclic redundancy check (CRC) –
performs a division calculation on the
entire block of data to produce a 16- or
32- bit result. Like check sum, CRC is a
block error detection method and cannot
reveal which byte or bytes in a block are
faulty.

14. Examples of Communication
Systems

15. - E-mail
- Voice Mail - Fax
- Smart Phone - Instant Messaging
- Teleconferencing - Video-conferencing
- Groupware - Telephony
- E-Commerce - The Internet
- Bulletin board system - The Web
- Global positioning system

16. ▪Teleconferencing (as
an alternative to a face
to face meeting) – or
videoconferencing,
allows people in
different locations to
participate in meetings
without the problems
and expense of travel
using microphone and
a camera, monitor and
speakers.

17. ▪ Teleconferencing
▪ How audio data is
transmitted and received –
Sound and images must be
converted into binary by
digitising before it is
transmitted.
▪ How video data is
transmitted and received –
images and sounds can be
represented as a series of
numbers and therefore 1s and
0s. The process of converting
images into binary numbers is
called digitisation.

18. ▪ Teleconferencing
▪Advantages – reduction of
costs due to decreased travel
and accommodation bills,
stimulates face-to-face
meetings without travel.
▪Disadvantages –
teleconferencing results in
the lack of personal contact
which limits the potential to
develop interpersonal
relationships.

19. Examples of teleconferencing
such as:
▪ Business use –Business use of
teleconferencing is becoming common
as meetings and conferences can be
held in any city nationally or
internationally without the need for all
participants to b in the same location.

20. Examples of teleconferencing such
as:
▪Distance education –. Unlike a video
lecture, teleconferencing is interactive as
it allows the participants to ask and
answer questions. Student living in these
remote areas can participate in
teleconferences, lecture broadcasts and
live tutorial sessions.

21. ▪ Electronic commerce
▪ EFTPOS as the transfer of funds
electronically at the point of sale –
Electronic Funds Transfer – Point
of Sale – is an increasingly popular
method of purchasing goods and
services using a credit card or
savings account. The customer
swipes the card through EFTPOS
terminal, choosing and account and
entering their PIN as a password. The
funds are transferred from customer’s
account to retail store’s account
without any cash being handled which
is an advantage.

22. ▪ Electronic commerce
▪ Electronic banking on the
Internet – E-commerce (electronic
commerce) involves conducting a
business and making sales over a
network such the Internet making ii
convenient for customers to
purchase goods as they ‘browse’
as many stores at they want 24.7
without leaving their home.

23. Transmitting and receiving in
communication systems:

24. Communication concepts including: -
▪Protocols – a protocol of
information exchanged by describing
parameters such as speed of
transmission (bps, baud),
transmission mode (answer or
originate), handshake, parity, error,
detection and correction.
Examples include: Exports-modem,
Z-modem, smtp, http and NETBIOS.

25. Communication concepts including:
-
▪Handshaking – is the process by
which two devices initiate
communications. It enables a
communications protocol to be
agreed upon. Bandwidth (bps) is
a measure of how much
information can flow along a data
pipe.

26. Communication concepts including: -
▪Error detection / correction – Error
correction methods – these protocols
attempt to correct any detected
transmission errors. Retransmission is
where the receiving computer requests that
part of the message to be sent again and it
may involve only the corrupted blocks of the
message being transmitted or the whole
message being transmitted. Retransmission
is the most common error correction

27. Serial Transmission
Data is transmitted, on a single channel, one
bit at a time one after another
often used to send data to a printer
-
Sender Transmitted Receiver received
101 0 0 1 1 0

28. Parallel Transmission
-each bit has it’s own piece of wire along which it travels
- Much faster than serial because of way bits processed.
Receiverreceived
Sendertransmitted
1
0
0
1
1
0
0
1
All bits are sent simultaneously

29. Simplex: One
direction only
Transmission Direction
Half duplex: Both
directions but only
one direction at a
time

30. Full duplex:
send and
receive both
directions at
once

31. RING – consists of nodes in a
closed loop or circle. Each
node is part of a loop
linking all the nodes
together and nodes are
attached to the cable at
various points around the
ring. Traffic can be one-way
around the loop or can
travel in both directions if a
double loop is used.
3 Types of LANs

32. RING – Its advantages
include: a single cable is used to
connect all the nodes making it
extremely cheap, takes up less
space and easy to fault-find in
terms of broken cable.
Its disadvantages include: if
the ring is broken or cable is
faulty the network ceases to
operate, the ring must be broken
to add or remove nodes, and it’s
slow as it goes around the entire
circle.
3 Types of LANs

33. 3 Types of LANs
STAR – is a network topology
that consists of computers
attached to a central point or
node (a device such as a
computer connected to a
network) which can be a
computer like a mainframe,
hub with links going out to
computers that are
workstations and servers. Star
networks are popular and
most common in LANs.

34. 3 Types of LANs
STAR – Its advantages include: each
node has its own cable and doesn’t
need to share the line with other nodes,
if a cable to a node is broken then only
that node is affected while the rest of
the network can operate normally, new
links to the central node can be easily
added or existing links easily removed
without affecting the rest of the network.
Its disadvantages include if the
central node fails then the entire
network will cease to operate, more
cabling is needed than for other network
topologies which is uneconomical.

35. BUS – this uses a cable in single line with two end
points. At each end point there is terminator that
prevents signals at the end of the cable from
being reflected back into the network. In a BUS
network each node is connected to a single cable
and it is mostly used for small LANs.
3 Types of LANs

36. BUS –Its advantages include: it’s easy and cheap to set up as
it requires less cables, nodes can be easily added and
removed and if a node goes down the network is unaffected.
Its disadvantages include: because the one cable
carries all the data, collisions (data traffic jams) become more
common as more nodes are added or when multiple terminals
transmit at the same time.
Nowadays, bus networks are often replaced with a star
3 Types of LANs

37. Network Hardware – a PC needs specialised
hardware to become part of a network which includes
a network card and cables.
▪ Servers – a computer that supplies a service to other
nodes on the network, taking a responsibility for
certain tasks such as file sharing, printing, and
database and Internet access to network to users.
1.File Server – computer dedicated to the task of
sharing disk space, files and sometimes a printer. It
uses the NOS to allowing many registered users to
access files and programs at the same time.
2.Print server – computer that manages printing
tasks whereby printers are attached to them and
can be accessed by all network users in the
network environment.

38. ▪ Servers –Mail server – this computer stores,
receives and distributes electronic mail for
users.
1.Web server – computer that stores and
‘serves’ webpages to users on either
intranet or the internet.
2.Proxy server – this computer acts as a
temporary store for data moving between
LAN and other network like the Internet.

39. NETWORK TOPOLOGIES (categorizing by shape)

40. Other information processes in
communication systems

41. Collecting
refers to the process of obtaining data from a source external to
the system. Data can be collected in either digital or analog
form. A computer can directly process digital data but needs to
digitise analog data before attempting to process.
▪ The phone as a collection device with voice mail –
the callers are: given a series of options then requested to
press a key on the phone’s keypad corresponding to their
chosen option used in bill payment and product ordering
systems and caller has to enter their credit card number
allowing entered data to be immediately digitised and
processed by computer.

42. Collecting (continued)
▪ EFTPOS terminal as a collection device for
electronic banking –
(Electronic Funds Transfer- Point of Sale) is a
collection device for electronic banking and can be
used for: to pay for a purchase customer selects
the account type (credit, savings or cheque) enters
their PIN and amount is directly withdrawn from
customer’s bank account or added to their credit
card statement

43. Processing
this is an information system process that converts digital data
into information within the information system.
▪ Sending of attachments with email – an email
(Electronic Mail) is the transmission of memos and
messages over a network. Users can email to a
single recipient or broadcast it to multiple users.
Attachments are computer files such as text,
video, sound pictures or programs sent with an
email message.

44. Processing (continued)
this is an information system process that converts digital data
into information within the information system.
▪ Encoding and decoding methods –
communication systems frequently convert data
signals between analog and digital. The parts of a
communication link that use analog signals (e.g.
from telephone to local exchange) must convert all
data to analog before transmission.

45. Processing (continued)
this is an information system process that converts digital data
into information within the information system.
▪ Client-server architecture – shares the
processing between client and server computers
on a network.
▪ Client controls the user interface and
application logic – the processing in client server
networks is shared or distributed between server
and client.

46. Processing (continued)
this is an information system process that converts digital data
into information within the information system.
▪Server controls access to the database –
sometimes more than one user wants to access
the same data record at the same time. The
database software at the server can lock those
records in use.

47. Displaying
is the process by which the information stored
within the system is made available for its users.
This is a necessary process within a
communication system as it produces the output.
▪ The phone as display device with voice mail – a telephone is a
display device for voice mail as the output is audio, not graphical. A
caller’s telephone number and name can be recalled on the screen of a
mobile phone.

48. Displaying (continued)
is the process by which the information stored within
the system is made available for its users. This is a
necessary process within a communication system
as it produces the output.
▪ EFTPOS terminal as display device for electronic banking – the
EFTPOS terminal will display the type of account user has selected, amount
of cash to be withdrawn / amount to spend on the transaction. It asks for pin
number, display processing messages and then whether the transaction has
been approved or not.

49. Issues related to communication
systems

50. ▪ Usage of communication systems to
share knowledge not just data – main role
of communication systems is to share
knowledge. Most communication systems
are privately controlled an owned thus these
powerful organisations and individuals
control the information they pass on to
receivers who also have control over the
knowledge.

51. ▪ Issues related to messaging systems – increasing business and
personal communications occur via email or other Internet messaging
solutions like chat rooms or instant messaging clients.
▪ Ideas delivered by this means appear less forceful and
caring than ideas delivered personally
▪ Danger of being misinterpreted
▪ Power relationships – communications via electronic means
restrict relationships as inter-personal socialisation is limited.
▪ Privacy and confidentiality
▪ Electronic junk mail – this is one a user receives countless
unrequested emails from unknown people or spammers.

52. ▪Implications of Internet trading
including – purchasing goods and
services over the Internet has
become common recently with
payments transacted via a credit
card. In today’s ‘cashless’ society,
even people low on cash can
purchase goods via a credit card, an
EFTPOS terminal or instant credit
checks, encouraging spending but
resulting in increasing debt levels.

53. ▪Trading over the Internet and its
commercial implications – many
businesses which are based entirely on
the Internet may have a great website
and product but have neglected to plan
their supply chain as thoroughly and
thus consumers face lengthy delays
when purchasing items.

54. ▪ Difficulties of censoring content on the Internet – censorship is a
major issue concerning control of the Internet where its contents
(inappropriate websites, newsgroups, emails, chat rooms) should be
censored but because the Internet is worldwide the responsibility of
censorship becomes a problem whether the user, content provider or
ISP (Internet Service Provider) should be responsible.

55. ▪ Issues arising from Internet banking
including:
▪ Security of banking details – Internet banking
customers have a right to the privacy of their
transactions and financial details. When
account details are entered into a response
form on a webpage, the user has no control
over the computer systems it passes through
before reaching its destination. The encryption
(data security coding) systems used on many
web browsers and web servers aren’t totally
secure as many have been broken by

56. ▪ Issues arising from Internet banking including:
▪ Changing nature of work – jobs have been
eliminated due to increased Internet emphasis.
Replacements generally require skills in IT and
web support services causing the existing staff to
retrain or find alternative jobs.

57. ▪ Issues arising from Internet banking including:
▪ Branch closure and job loss –This has had a
major impact on customer access to traditional
banking services, has increased customer
dissatisfaction with the banks and reduced
employment in the banking industry.

58. The emerging trend of accessing
media such as radio and video
across the Internet –
communication technologies are
converging into one technology –
‘convergent technology’ - as
multimedia and the Internet have
already converged, radio and TV
has started to converge with the
Internet through live audio and video
Internet broadcasts. ….

59. The web has started to converge with
cable TV with the provision of fully
interactive cable broadcast services and
web services are now appearing on
broadcast digital TV. Telephones and
mobile phones can now purchased with
high resolution LCD screens and built-in
web browser and email software while a
PC is no longer needed to access the
Internet with set top boxes that turn the
TV into a web browser.

60. Issue maybe compatibility of site for mobile devices
DESIGN AND TECHNICAL CHALLENGES FOR MOBILE WEBSITE CONTENT
The issue of mobile accessibility emerges in every
realm of creating a website, affecting the size and
type of images you embed, the color scheme you
apply to your site, and what kind of navigational
structure you choose. READ MORE
• Media queries
• jQuery Mobile
• Small viewports
• Lighting and color issues
• Download speeds
• Mobile plug-ins (and lack thereof)

61. Issue maybe compatibility of site for mobile devices
•Limit graphics: Graphics are an excellent way to spice up a Web site, but their use is
questionable when working with small screens. Also, many handheld devices feature monochrome
displays, so rich color graphics are lost. The most important text or information should take center
stage. If you must use graphics, limit their size to control download times. In addition, effectively use
every pixel of a graphic and avoid unnecessary elements. On a final note, take advantage of the alt
tag for images so graphic functionality is conveyed when/if images are not displayed.
•Limit download times: Travel back in time to the initial days of the Web where dial-up
connections with a 9,600 baud modem was cutting edge, and you will understand the bandwidth
limitations for wireless devices. So, you should develop scaled-down pages that eliminate the bells
and whistles and deliver only what is necessary to mobile clients.
•Carefully select content: Tailor the content specifically to the target user group by
displaying only the most essential data.
•Minimize page length and size: Scrolling on handheld devices is often limited,
awkward, and hard for users to keep track of their place with scroll keys and other pen input devices.
With that in mind, you should limit the amount of scrolling required in a Web application. This may
involve splitting normal pages into multiple pages for handhelds. Architecting the site for handheld
devices demands information that is effectively organized to maximize user experience.
•Utilize standard HTML: Stick with standard HTML tags to ensure proper functioning of
an application.

62. Processes involved with Mobile Device
Collecting : This would be carried out by the physical
interface of Camera, Microphone and Qwerty Keypad
Analysing : This is when the data collected from
the user is made into useful information.
Transmitting & Receiving : This would be carried
out using GSM, via Wireless in Cells or Satellite
Display : This is carried out by a LED screen depends
upon the number of pixels that it displays. Also Audio
is available.

63. Digital Twins
Digital twin refers to computerized companions
of physical assets that can be used for various
purposes. A digital twin uses data from sensors
installed on physical objects to represent their
near real-time status, working condition or
position.
By creating digital twins of assets like turbines and
generators, GE researchers are able to fine-tune their
operation and gain valuable insight about their
lifecycles.

64. Digital Twins
Digital twin is “real time” and would rely on a
continuous data transfer , security is also
Important.
Fast connectivity and powerful processing over
Optic fibre would be ideal. Software and
Hardware is required.
Use of sensors such as temperature, movement
In the case of the engine are required.

65. Processes involved with Digital twins
Collecting : This would be carried out by sensors
Analysing : This is when the data collected from
the sensors is made into useful information.
Transmitting & Receiving : This would be carried
out using preferably Optic Fibre or may be done
by Wireless, in the case of remote Twins
Storage & Retrieval is collected from the real
Device and stored for use in simulation with the
digital device