1. 6.1. Communication Methods Revision using Qwizdom

2. Data Communication - Revision What is SERIAL data transmission: A.A method to exchange signals between devices that communication with each other B.One character is sent as soon as it becomes available C.Bits are sent one at a time over a single wire from source to destination D.Several bits are sent simultaneously down many wires at the same time

3. Give one advantage of serial over parallel transmission A.Can be transmitted over a longer distance B.Is suitable for short distances e.g. from PC to a local printer C.Data can be skewed

4. Which form of data transmission method is this A.Parallel B.Synchronous C.Asynchronous D.None of the above D

5. Identify the start bit A B C D D

6. One character is sent and received using Asynchronous transmission without errors. Is this odd or even parity? A. odd B. even D

7. What is meant by baudrate? A.The number of bits per signal B.The number of bits transmitted per second C.The range of frequencies on which a medium can transmit D.The number of signal changes per second

8. Parity is used to check A.For a correct baud rate B.The accuracy of transmission C.The length of transmitted data D.That the stop bit is correct

9. True or False  Bit rate is often lower than the baud rate

10. True or False  Bandwidth refers to the range of frequencies that a medium can transmit

11. True or False Using even parity, has this byte been corrupted during transmission? 01000010

12.  A computer word contains the bit pattern 00010111  What is the decimal if it represents a pure binary number A.43 B.17 C.23 D.18

13. A computer word contains the bit pattern 0001 0111 What is the hexadecimal value of this binary pattern? A. A3 B. 17 C. 23 D. 1A

14. 6.2. Network Environments

15. What is a local area network? A.Computers connected within one building B.Computers and peripherals connected over a specified small distance, in one building or one site C.Computers connected within one city D.Computers connected over a large geographically remote area

16. Communications Networks Local Area Network (LAN)  Collection of computers and peripherals confined in one building or a cluster of buildings  They are connected together by a direct, common electrical connection Wide Area Network (WAN)  A network in which computers are geographically remote.  A LAN can be connected to other LANs or to a WAN

17. WAN connections  Public switched telephone network  High speed, high-bandwidth dedicated leased lines  High-speed fibre-optic cable  Microwave transmission links  Satellite links  Radio waves  The internet

18. Examples of WANs  Mobile phone network. Circuit switching for voice calls Packet switching for text messages  These are piggybacked onto packets that mobile phone continually send so that bas stations can locate them.  Each packet has 160 bytes of spare capacity

19. Wireless  Find out: What kind of signals used for wireless? What is WI-FI? What is WEP? What is WPA? What is Bluetooth?

20. Wireless Networking  WAP (wireless access point) using Radio frequencies  Allows data to be relayed between the wireless devices and wired devices.  WAN WI-FI = standard / trademark  WEP (Wired Equivalent Privacy)  WPA (WI-FI Protected Access)  LAN Bluetooth – short distances (PAN – personal area networks) 1 Mbps Data is chopped up and sent using up to 79 frequencies

21. Internetworking  LANs connected by a WAN so they can communicate  E.g.  ARPANET  internet

22. Advantages of Networks  Allows sharing of resources Disk storage, printers, image scanners, modems, central servers  Allows sharing of information held on disk drives accessible by all users  Easier to store application programs on one computer and make them available to all users.  Allows electronic mail to be sent between users  Easier to set up new users and equipment  Allows connection to different types of computer which can communicate with each other

23. Disadvantages  Users become dependent on them  If network stops access to various hardware and software may not be possible  Efficiency of network is very dependent on the skill of system manager  Difficult to make network secure against hackers, novices, or industrial espionage  As traffic increases on network, performance degrades unless it is properly designed

24. What is a disadvantage of a network A.Difficult to share resources software B.Difficult to make network secure against hackers C.Difficult to set up new users D.Difficult to connect to different types of computers