 | Term | Definition |
| |
enables people to send and recieve data and info. |
What do communication systems do? |
| |
Telephone,radio and television |
Examples of communication Systems |
| |
1. Data Source 2. Transmitter 3. Transmitter Medium 4. Receiver 5. Destination |
Components of communication system |
| |
Produces the data to be sent |
Data source |
| |
encodes the data into a signal suitable for a transmission medium |
Transmitter |
| |
Channel, such as cable in which the signals are transmitted to destination. |
Transmission Medium |
| |
Decodes the signal back into the origina; data |
Reciever |
| |
Reciever of the Information |
Destination |
| |
See page 76 |
How is ATM a communication System? |
| |
Accurate, reliable, and secure transmission mediums |
What are 'good' communication systems? |
| |
1. Protocol 2. Handshaking 3. Speed Of Transmission + 4. Error Checking |
What factors do good commun. depend on? |
| |
Set of rules that governs the transfer of data between computers |
Protocol |
| |
defines how info. is transmitted and how errors are detected |
How 'protocol' works? |
| |
Otherwise, data transfer may be unsuccessful |
Why 2 computers must use the same protocol? |
| |
An internationally accepted standard to which protocols are written into. |
OSI reference model |
| |
divides data commun. into 7 layers.Each layer expresses standard [which uses a protocol].Bottom layer= transfer of data 4m one place 2 another.[type of plug,the format of data,the method of transmission and error checking.].Top Layer= Examines exchange of data bet. application programs.[Include prtcls that specify file transfer,passwords +network management. |
Describe OSI reference model |
| |
Only handshaking makes it possible |
How is data successfully transferred between devices? |
| |
An agreement made about which protocol to use in order for exchange of info to occur |
Handshaking |
| |
A series of signals that flow between devices during data transmission |
What does handshaking involve? |
| |
To indicate the type of protocol to be used |
Why handshaking process sends signals? |
| |
When two comp. handshake successfully. indicate da type of protocol |
When is a connection between two computers made? |
| |
Uses cables, such as wires. This is for devices which are closely linked to a cable. |
Hardware Flow Control |
| |
Uses a special code sent with a data. Used for long distant communi. |
Software Flow Control |
| |
Via transmitting device + bandwidth |
How is the Speed of transmission determined? |
| |
Fibre-optic cable- when cable television is transmitted thru fibre-optic cable, many diff. channels cn be tranmistted at the same time. |
Give an example of a high ranged bandwidth . |
| |
1. Bits per second 2. Baud Rate |
How is the speed of data transmission measured? |
| |
Max. number of bits that can be transmitted in 1 sec. Includes special bits used in asynchronous transmission + any error checking bits. BPS also called ' bit rate' |
'Bits per second' |
| |
Max. number of data symbols/signals transmitted in 1 sec. |
Baud rate |
| |
Baud rate transmits data symbols in sec. A data symbol may contain more then one bit. |
Why are ' baud rate' + ' bps' dissimilar? |
| |
1. Errors in encoding and decoding data. 2. Interference with signals |
What causes errors when data arrives at its destination? |
| |
Error first must be detected and then corrected |
So how could error in data transmission be solved? |
| |
1. Parity Checking 2. Checksum 3. Cyclic Redundancy Check |
What are the common methods for error detection? |
| |
Uses an additional bit called a 'parity bit' to check for errors. This depends on the type of parity [even/odd] chosen and selection of the end bits is chosen accord.see pg 78 |
Identify 'Parity Checking' + Desc. |
| |
to ensure that the bits being tranmitted have actually arrived successfully |
What is the purpose of the 'additional bit' in parity checking. |
| |
It check for errors by adding the number of bits in a data packet.The sum of the data bits in a data packet is attached to the data packet. If the same answer is produced within the reci. device then there is no error |
'Checksum' |
| |
By dividing the total data into smaller groups. |
How is the data packet in checksum method created. |
| |
Uses a division process to check errors. First of all the data is divided into predetermined lengths + divided by a fixed divisor. Then the remainder of the calc. is attached and sent with data. When data recieved then remainder is recalculated. |
Cyclic Redundancy Check |
| |
These can be changed by the user tyo ensure a connection between 2 devices. Settings are often 'parameter' |
Communication Settings |
| |
any variable being given a constant value for a part. application. |
'parameter' |
| |
1. bits per sec. 2. Data bits. 3. Parity 4. Stop,Start bits 5. Flow Control [ see pg79 4 diagram+desc] |
What are some common paremeters that are used to connect 2 computers? |
| |
Teleconferencing, messaging systems and electronic commerce |
What are the 3 examples of communication systems? |
| |
Use of an electronic transmission to allow ameeting to occur at the same time in different locations. Alternative to face-to-face meetings |
Teleconferencing |
| |
refers to communication, such as audio conference or a video conference, that goes beyond the normal telephone call between two people |
What does teleconferencing refer to? |
| |
Single telephone line involving 3 or more people at different locations. Service prvded by telephone cpmpany. It is transmitted and recieved using existing telep. lines. |
Audio conference |
| |
A meeting that allows people in different locations to see video image of each other on a screen, as well as hear speech. |
Video Conference |
| |
-Stimulates face to face meeting + reduces costs. Money is saved by not buying airfares,hotel rooms and meals. Saves time and energy invlved in travelling to attend facetoface meeting. Used in business and distance education. |
Advantages of teleconferencing |
| |
Removes the interpersonal relationship achieved through a facetoface meeting. this is disad. bqz physical contact and informal discussions are often needed to clarify ideas and develop partnerships |
Disadvantage of teleconferencing |
| |
Used to send messages to people in diff. locations who may receive the message at later time. |
Messaging systems |
| |
Creation, storage, exchange and management of messages |
What does a messaging system involve? |
| |
1.Traditional systems [ Telephone,fax] 2. Voice Mail 3. Electronic Mail |
What are the types of messaging systems? |
| |
page 81 Heinemenn |
Telephone [ Messaging system] |
| |
pg 81 , Heinemenn |
Fax |
| |
pg 82,hein |
Voice Mail |
| |
pg 82, heinemenn |
Electronic mail |
| |
Is the buying and selling of goods and services via the internet |
Electronic Commerce |
| |
24 hour availability , global reach, the ability to interact and prvde costumer info. and a multimedia env. |
What does E-Commerce provide? |
| |
computer products, books, gardening products, music, or office supplies. |
What does the most popular e-commerce site sell ? |
| |
EFTPOS ; ELectronic Banking |
Types of Electronic Commerce |
| |
Electronic Funds Transfer At Point Of Sale [ hein. pg85] |
EFTPOS |
| |
Hein pg85] |
Electronic Banking |
| |
Refers to the transfer of data and info. It is carried put using numerous commun. concepts and completed by netwrok hardware and software |
What does 'transmitting and receiving' refer to? |
| |
-Transmission of data - Protocols + Handshaking - Networks-Network Topologies - Network Access methods - |
What does communication concept include? |
| |
Network Interface card - Servers - Routers and switches - Gateways and bridges -Hubs -Transmission Media |
What do network Hardware consists of? |
| |
-Network operating systems. -Network operating system tasks - Logon and logoff procedures |
What do Network Softwares consist of? |
| |
Data is transmitted bet. devices in 2 ways: Serial Transmission and Parallel transmission[ Heinmenn pg 87] |
How is data tranferred bet. devices ?Parallel ; Serial; Asynchronous; Synchronous |
| |
-Simplex Mode - Half duplex mode - Full Duplex mode [ Hein. pg 88] |
What are the direction of data flow? |
| |
hein.pg 88 |
Prtcl + handshaking [comm. concept] |
| |
pg89hein |
Common data transfer protocol |
| |
number of comp and their peripheral devices connected together in some way. |
Network |
| |
Each device in a network |
Node |
| |
diff. types of devices such as printers, storage devices, terminals and workstations |
What could a node in a device be? |
| |
are devices[could be comp] that send data to and receive data from another computer system. |
Terminals |
| |
When a terminal has both memory and processing capabilities |
Intelligent terminal |
| |
Most personal comp r classified as intelligent terminals and are called workstations on a network |
Workstations |
| |
This is when a computer is connecteddirectly to another computer, using a cable. |
Simplest form of a network |
| |
Local area networks and Wide area networks |
What are networks classified as |
| |
Hein.pg90 |
Local Area Networks [LANS] |
| |
hein og 90] |
Wide Area networks [WANs] |
| |
mainframe computer in a WANs |
Host |
| |
Offers higher transmission spee.d + more accurate transfer of data than those available through the public switched telephone network.[PSTN]. PSTN links are rel. cheap if computers do not require constant connection.Howver, PSTN links are not guaranteed and can be interrupted |
Private Leased line |
| |
Packet Switching |
What does most data which is sent over network uses? |
| |
it is a technique that divides messages into small data packets, transmits the packets and later joins the packets to form original message. |
What is 'packet switching' |
| |
Allows multiple usrs to use the same transmisson line by interspersing[ to scatter here and there or place at intervals among other things] the data packets from diff. users. |
Purpose of packet switching |
| |
May not be sent along the same path and could arrive at the destination at diff. times and in wrng order |
Disadvantage of data packet |
| |
an address and control instruction to reassemble the message in the correct order. |
What does each data packet contain? |
| |
Packet Switching |
What is the data transfer on the internet based on? |
| |
Physical arrangment of the devces in a network. see hein.pg 91 for diagram |
Network Topology |
| |
see hein pg 91-2 |
Types of network top. |
| |
Deals with multiple users who are wanting to acciess the network at the same time. |
Network Access Methods |
| |
1. Ethernet 2. Token Ring [ hein.pg92] |
Describe two network acess methods |
| |
-Network Interface Card 2. Servers 3. Routers And Switches 4. Bridges And Gateways5. Hubs 6. Transmission Media. These all r needed in order to successfully construct a network |
What are the network hardwares? |
| |
It is required by each comp. which is connected to a network. |
Network Interface Card |
| |
A network cable and have connectors on the card for different types of cables. |
What does most NICs require |
| |
Type of networks. NICs package data according to the rules of the network operating system and transmit data along the connecting network cable. |
What does the type of NIC depend on? |
| |
A computer that prvdes services to other computers on the network. |
Servers |
| |
Individual comp. log onto the server, which gives them access to files, applic. or peripheral devices. |
How servers work |
| |
hein.og 93 |
What are the different types of servers? |
| |
Devices used to determine paths between networks.pg 93.Hein. |
Router and switches |
| |
It needs networks to be linked to other networks, paths to be established between the networks and signal strength to be boosted. |
What is needed in order for data to travel between networks? |
| |
The actual linkage between networks is achieved using devices such as those. hein.pg93-4 |
Bridges and Gateways |
| |
A signal may be corrupted due to long distances or interference from electromagnetic fields. A repeater is used to rebuild a fading signal to its orginal strength and shape b4 transmitting it onwards.It ensures that the data is received just like as it was sent. |
Repeater |
| |
Used in LAN to connect network segments. Repeaters are less intelligent than a bridge and gateways |
Where is the network repeater used? |
| |
hein 94 |
HUb |
| |
Along a transmission device |
How is the data transferred? |
| |
The capacity is called bandwidth and is measured in bits per sec. |
How is the capacity of the transmission device measured? |
| |
Transfers data through wires and cables. These cables must be protected from damage , they take up space and they can be difficult to install. |
Wire transmission |
| |
Carry large amount of data with little interference from other signals. |
Adv of wire transmission |
| |
- Twisted Pair - Coaxial Cable - Fibre Optic Cable [ Hein.pg95] |
What are the cables involved in wire transmission? |
| |
bqz fibre optic cable is usually too expensive and difficult to install |
Why most lans use twisted cable or coaxial cable but not fibre optic cable |
| |
Baseband [ntwrks use the entire capacity of the cable to trnsmit only 1 signa; at a time. Most LANs are baseband.] Broadband - networks divide the cable so that the several sgnals cn be trnmtted at the same time. |
What are the two types of transmission? |
| |
moves data through air and space. Radio and tv are an example. |
Wireless transmission |
| |
hein.pg 95 |
What do wireless transmission invlve? |
| |
Contains rules for communi. + determines how the ntwrk devices send and recieve data, |
What do network softwares cntain? |
| |
by a network administrator |
How is the network software organised? |
| |
hein.pg 96 |
Responsibiltiies of network administrator? |
| |
Completes network admin. responsibilities.heinpg96 |
Network operating systems |
| |
Hein. pg98 |
Intranets + extranets |
| |
Collecting, processing and displaying. Hein.og 100-1 |
What are the info. processes that play a major role in communication systems? |
| |
pg 104-108 |
Social and ethical issues raised by commun. systems? |
| |
- Analog data to analog signal. - Digitial data to analog signal - Digital data to digital signal-Analog data to digital sgnals |
What are the four encoding and decoding possibilities in transmission? |
