6.1. Communication Methods Revision using Qwizdom

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

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

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

Identify the start bit A B C D D

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

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

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

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

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

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

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

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

6.2. Network Environments

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

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

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

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

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

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

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

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

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

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