Role of Communications Systems

1
Role of Communications Systems

• AS Module 1 10.6
• Heathcote Ch. 6

2
Introduction

• The information age
• Made possible by development of
  telecommunications
• Modern business dependent upon telecommunications
• Telephone
• Fax
• Various computer links
• Public lines
• Private cables
• Microwave
• Fibre-optic links
• Satellite

3
Communication systems

• The Internet
• LAN (Local Area Network)
• WAN (Wide Area Network)
• The World Wide Web
• On-line information services
• Electronic bulletin boards
• Intranets

4
The Internet

• Essentially an enormous WAN
• LAN Local Area Network
• WAN Wide Area Network connects computers and
  networks over a large geographical area
• Developed from ARPANet US Department of Defense
  late 60s
• Creators first to see computers as communication
  devices rather than just processing devices
• No central governing body
• No control of content
• Continues to grow at phenomenal rate
• http//www.netsizer.com/
• Millions of users at any one time

5
The World Wide Web

• A collection of pages stored on computers
  throughout the world joined by hypertext links.
• A link may be text or graphics
• When you click upon them you be taken
  automatically to a related web page
• Access provided and facilitated by browsers such
  as Netscape or Internet Explorer
• Creation attributed to Tim Berners-Lee in 1989
• http//www.wired.com/news/technology/0,1282,31830,
  00.html

6
On-line Services

• Information-based
• News, share prices, weather and sport
• Service-based
• Banking
• Shopping
• Education
• Entertainment
• Databases

7
Bulletin Boards

• Information exchange and discussion areas
• Set up by
• Academics
• User groups
• Also used for illicit activities such as
  terrorism and paedophilia

8
Intranets

• Essentially a private internet
• Set up by companies or schools
• Allow sharing of information
• Documents
• Databases
• Applications
• Microsoft Office software allows businesses to
  view documents as web pages

9
Electronic mail (E-mail)

• E-mail has many advantages over both ordinary
  mail and the telephone. For example
• A message can be sent from your desk to anywhere
  in the world at the price of a local call
• The same message can be sent simultaneously to a
  group of people
• The message will arrive in at most a few hours,
  and can be picked up the next time the recipient
  looks at their e-mail
• It is easy to send a reply to an e-mail as soon
  as it is received or forward it to someone else
• Long files including video, sound and graphics
  can be sent automatically when the cheap rate
  starts after 6pm
• Graphics and text can be electronically
  transmitted and placed in a document by the
  recipient

10
Accessing the Internet

• Basic hardware requirements
• Computer
• Telephone line
• Standard line is cheapest option theoretically
  up to 56K bps (bits per second)
• ISDN (Integrated Subscriber Digital line) 128K
  bps
• ADSL (Asymmetric Digital Subscriber Line) 8M bps
  downstream, 640K bps upstream
• Modem (Modulator/Demodulator) for analogue lines
• Telephones designed for speech (analogue signal)
• Modems at either end convert digital-analogue and
  then analogue-digital.

modem
modem
11
Accessing the Internet

• Basic software requirements
• Connection via an ISP (Internet Service
  Provider)
• Software package
• Browser
• Comms. Software (TCP/IP protocol)
• E-mail
• FTP client for downloads and uploads
• Newsreader to allow access to Usenet groups

12
Telephones

• Mobile phones are just about normal for everyone
  now
• 42 of UK households in 1999
• 65 of UK households by end of 2000
• Source http//www.rcb.dk/uk/staff/chm/wap.htm
• WAP services have not hit expected heights
• One-offs such as Big Brother did dramatically
  increase usage

13
Facsimile transmission (Fax)

• Indispensable to even the smallest business
• Greatly speeds up business transactions
• Scans and digitises images (text or graphics)
• Transmits them in analogue form over a telephone
  line to another fax machine, which then produces
  a copy of the image on a piece of paper

14
Advantage of Fax

• Send documents e.g. orders, newspaper cuttings,
  maps, instantly
• Send overnight at cheap rate
• Written evidence with signature
• No need for recipient to be there, unlike phone
• For example, can book a car / hotel in Uganda
  with ease and get immediate confirmation

15
Disadvantage of Fax

• Paper jam
• Runs out of paper / ribbon (when youre away)
• Attracts junk faxes

16
Voicemail

• A sophisticated answering machine
• Various services or departments available when
  you press a particular key
• Messages can be directed to individuals who are
  absent
• Messages can be cleared or forwarded

17
Teleconferencing

• Allows people in different locations to exchange
  ideas and information interactively
• Most basic form
• Telephone or e-mail
• More advanced videoconferencing
• Video cameras
• Microphones
• Large monitors
• Computers
• Codec required to convert and compress analogue
  video images and sound waves into digital signals
  to transfer over digital telephone lines
• High-bandwidth required (at least ISDN)
• Bandwidth is a measure of how much data can be
  passed down a line