Communication Systems (1 Viewer)

LittLe_DeviL

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This will contain information about Communication Systems. I will post notes myself about this topic, any arguments you have about what I or anyone else has said, feel free to express them. If you have information on this topic which may be helpful, please feel free to write it here...
 

LittLe_DeviL

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Characteristics of communication systems

A communication system enables people to send and receive data and information.

All communication systems have five basic components:
1 The data source produces the data to be sent.
2 The transmitter encodes the data into a signal suitable for a transmission medium.
3 The transmission medium is a channel, such as a cable, in which the signal is ytansmitted to the destination. The signal may be changed or distorted during transmission.
4 The receiver decodes the signal back into the original data or an approximation of the data.
5 The destination is the receiver of the information.
 

LittLe_DeviL

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Protocols

A protocol is a set of rules that governs the transfer of data between computers.

The OSI reference model divides data communication into seven layers.
 

LittLe_DeviL

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Handshaking

Handshaking is an agreement about which protocol to use to accomplish the exchange of information.

There are two methods of handshaking to control the flow of data:
Hardware flow control uses a dedicated connection, such as a wire.
Software flow control uses a special code sent with the data.
 

LittLe_DeviL

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Speed of transmission

The bandwidth is the capacity of the channel, or tansmission medium.

The speed of data transfer is measured by the number of bits per second or by the baud rate:
Bits per second (bps) is the maximum number of bits that can be transmitted in one second. Bps is also called the bit rate.
Baud rate is the maximum number of data symbols or electrical signals that can be transmitted in one second.
 

LittLe_DeviL

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Error checking

Three common methods for error detection are parity checking, checksum and cyclic redundancy check:
Parity checking is a method of checking for errors in data transmission using an additional bit called a parity bit.
Checksum is a method of checking for errors in data transmission by counting the number of bits in a data packet.
Cyclic redundancy check (CRC) is a method of checking for errors in data transmission using a division process.
 

mastermind

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Re: Protocols

Originally posted by LittLe_DeviL
The OSI reference model divides data communication into seven layers. [/B]
How much do we need to know about the OSI Reference Model??

Thanks
 

Nelly

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You just need to know that the OSI reference model divides the information into 7 layers. Each later expresses the standard, using a protocol
 

LittLe_DeviL

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Communication settings

A parameter is a variable that is given a constant value for a particular application.

Bits per second is the speed of transmission, such as 56000.
Data bits are the number of bits in each group of data.
Parity is whether the data contains a parity bit for error detection.
Stop/start bits are the number of stop and start bits used in asynchronous transmission.
Flow control is the software handshaking protocol, such as XON/XOFF.
 

LittLe_DeviL

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Teleconferencing

Teleconferencing is the use of an electronic transmission to allow a meeting to occur at the same time in different locations.

An audio conference is a single telephone call involving three or more people at different locations.
A video conference is a meeting that allows people in different locations to see video images of each other on a screen, as well as hear speech.
 
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LittLe_DeviL

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Messaging systems

A messaging system is used to send messages to people in different locations who may receive the message at a later time.

Traditional systems
A telephone is a system for transmitting sounds or speech between distant locations along telephone lines.
A fax, or facsimile, machine is a system of transmitting and reproducing documents by means of signals sent over telephone lines.

Voice mail
Voice mail, or v-mail, allows communication with other people by storing and forarding spoken messages.

Electronic mail
Electronic mail, or email, allows communication with other email users by sending and receiving electronic messages using a computer.

Email can be written to anyone who has an email address.

Most email messages contain two main parts: the header and the body of the message.

The header contains four main parts that the sender fills in as required:
Email address (To: ) is the address of the person receiving the message.
Carbon copy (Cc: ) sends the same message to other people apart from the main recipient (optional).
Blind carbon copy (Bcc: ) sends a copy to other people without revealing that these other people got the message (optional).
Subject is the topic of the message or a brief description.

The body of the message is typed using the email software or is imported or copied from a word processor.

The user can reply to an email message simply by clicking on the 'reply' icon.
Forwarding messages involves sending messages you received to someone else.

An address book is used to store email addresses.
A mailing list is a group of people who may want to receive the same messages.
A signature is several lines automatically appended to outgoing email messages.
 
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LittLe_DeviL

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Electronic commerce

Electronic commerce, or e-commerce, is the buying and selling of goods and services via the internet.

EFTPOS
EFTPOS (electronic funds transfer at point-of-sale) is a system that allows people to purchase goods and services using a credit or debit card.

Electronic banking
Electronic banking allows customers to view their account balances and transaction histories, transfer money between accounts and pay bills using Bpay.
 
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LittLe_DeviL

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What do you think?

HOW IS IT???
Would anyone care to comment if you think what I am doing is helpful, and what you think of the information, your input would be greatly appreated... Thankyou
 

mastermind

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Thanks little_devil for all this info. Its really good cos its refreshing my memory (its all either commonsense or in my head somewhere....ill start studying proper tonight!!) and clarifying things that maybe my school didn't cover - which is a lot....:D !

btw, thanks to u for the pm about OSI and nelly as well for the above info....
 
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Identify, describe and apply a specified communication protocol

An example of a communication protocol is TCP/IP. TCP/IP stands for transmission control protocol/internet protocol. It is the basic protocol of the Internet.

TCP- manages assembling of a message/file into smaller packets
IP- handles address part

Uses client/server model. Client requests something, server gives it to them

The protocol that we use to get on the internet is called Point to Point Protocol (PPP). These protocols encapsulate the IP packets so that they can be sent over the phone lines.
(http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214173,00.html)
 

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Identify, describe and apply a specified communication protocol

An example of a communication protocol is TCP/IP. TCP/IP stands for transmission control protocol/internet protocol. It is the basic protocol of the Internet.

TCP- manages assembling of a message/file into smaller packets
IP- handles address part

Uses client/server model. Client requests something, server gives it to them

The protocol that we use to get on the internet is called Point to Point Protocol (PPP). These protocols encapsulate the IP packets so that they can be sent over the phone lines.
 

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Servers
file servers
print servers
mail/web servers

Routers
Figures out where to send data packets
Table of available routs and conditions
Uses table and algorithms to figure otu best route
Can be used instead of a bridge or switch


Switch
Directs data packets along paths
Can also be a router
Does not have a map of netowrk
Can be faster


Hub
Centralises cable connections
Strengetens digital signals
Can include router

Bridge
HW and SW that links to two similar networks
often connects LANS with same protocol
Can be faster because same protocol

Gateway
HW and SW to link different types of networks
Also convert different protocols
 

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Transmission media

Twisted Pair
Unshielded
Shielded
Slowest medium, 60kps
long distances
phones

Coaxial
single copper wire surrounded by an insulator, grounded shielding and outer insulator
10Mbps
Few km

Fibre Optic
Light carries data, on off
less interference
fast ~400Mbps
expensive

Microwave
faster than twisted pair or coaxial
must have clear view
affected by wind and weather conditions
fast transmisison
large distances

Satellite
up in orbit around the earth
fast transmission
large distances

wireless LANs
short distances
signal easily affected

Mobile ophones
uses radio waves
good coverage
 

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Network software

Network Operating system
eg Lantastic, Win NT

Tasks
Administraiton
File Management
Applications
Resource management
Security

Intranet
private network
similar interface to web
consists many interlinked LANs
shares information and reosurces within organisation

Extranet
accessible to outside the organisaiton
 

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Acronyms

OSI: open systems interconnection
ACK: acknowledge
NAK: not acknowledge (used in transmitting data)
RTS/CTS: request to send, clear to send
XOn/XOFF: log on/log off
bps: bites per second
ASCII: american standard code for information interchange
CRC: cyclic redundancy check
CC: carbon copy
BCC: Blind carbon copy
ISP: internet service provider
EFTPOS: electronic funds transfer at the point of sale
POS: Point of sale
PIN: Personal identification number
FDDI: fiber distrubuted data interconnect
ATM: Asynchronous transfer mode
ATM: Automatic Teller Machine
TCP/IP: transmission contorl protocol, internet protocol
HTTP: hyper text transfer protocol
FTP: File transfer protocol
POP: post office protocol
MIME: Multipurpose internet mail extension
LAN: local area network
WAN: Wide area network
WANKER: IPT Teachers
PSTN: Public switched telephone network
CSMA/CD: Carrier sense multiple access, collision detection
NIC: Network Interface Card
NOS: Network Operating System
UTP: Unshielded Twisted Pair
STP: Shielded twisted pair
PPP: Point to Point Protocol
IIA: Internet Industry Association
URL: Uniform resource locator
DBMS: Database Management System
DFD: Data flow diagram
ERD: Entity relationship diagram
TPS: Transaction processing systems
DSS: Decision Support Systems
MIS: Management information systems
EIS: Executive information systm
RTA: Roads and Traffic Authority
CD-ROM: Compact Disk- Read Only Memory
1NF: 1st normal form
DKNF: Donamin/key nomal form
HTML: Hyper Text Markup Language
DVD: Digital vertasile disk (Syllabus calls it Digital Video Disk, but as any idiot knows, the 'V' stands for Vertasile.)
SQL: Structued Query Language
QBE: Query by example
AFIS: Automated Fingerprint identification system
GIS: Gepgraphic information system
TXT: text
BMP: Bitmap
JPEG: Joint photographic experts group
GIF: Graphic Interchange Format
MIDI: Musical Instrument Digital Interface
MPEG: Motion Pictures Experts Group
RTF: Rich Text Format
TIFF: Tagged Image File Format
PICT: Picture
EPS: Encapsulated Postscript
WMF: Windows Metafile Format
CGM: Computer Graphics Metafile
AIFF: Audio Interchange File Format
MP3: Motion Pictures Expert Group Layer 3
ADC: Analog to digital converter
DACL Digital to Analog converter
CBT: Computer Based training
VR: Virtual reality
WWW: World Wide Web
CRT: Cathode Ray Tube
LCD: Liquid Crystal Display
CODEC: Coder-decoder
DTP: Desk Top Publishing
IPT: Idiotic Prostitute teachers
 

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