Bill gates

networking transmission modes

computer network media refers to the means used to links or network nodes together. There are generally two types of transmission media, they are:-

1. bounded

2. unbounded

in bounded transmission media the connection between network nodes can be established with the help of different cables. This media also further divided into three categories. They are:-

a. twisted pair cable

b. coaxial pair cable

c. fiber optic cable

a. Twisted pair cable:-

It is normally consists of different wires. The individual pair has two wires that are separately insulted in plastic then twisted around each other and bound together in a layer of plastic coating anything’s shields outside the wire so, this type of wire is also called unshielded twisted pair cable (UTP). Some twisted pair wire is encased in a metal sealed & therefore is called shielded pair cable.

b. Coaxial pair cable:-

like the cable used in cable television system. Coaxial cable has two conductors. One is a single wire in the center of the cable and other is the wire mesh shield that surrounds the first wire. Coaxial cable can carry more data then older types of twisted pair cable.

c. Fiber optic cable:-

Fiber optic cable is made up of a thin glass that transmit data in the form of beam of light rather then electric current. Fiber optic cable can carry more then billions bits per seconds but it is too expensive.

Telecommunicating processors

these are devices , which support data transmission and reception between terminals and computers. These device sush as modems, multiplexers and front-end processors, perform a variety of control and support functions in a network. For example, they convert data from digital to analog and back, code and decode data,and control the accuracy and efficiency of the flow of data between computers and terminals in a network.

Front-end processors

A front end processors is located at the sit of the CPU or the host computer and it’s purpose is to relieve the central computer of some the communications tasks, leaving the larger computer free for processing appliations programs. Here we can see that communication processing and data processing equipment are nearly alike. Indeed, front-end processors are computers- they have some identical circuitry and perform many of the operations that a data processing equipment performs. The only difference between the two kinds of equipment is in their purpose.

Multiplexer,concentrators,and controllers

Like message switchers, a multiplexer allows severals terminals to use one line to communucate with a CPU. However, it allow the terminals to send their messages simultaneously. A multiplexer, in other words, collects message from various senders, put them in order, and transmits them along a broadband channel at very high speeds to the receiver.
A concentrators is essentially a smart multiplexer- it can be programmed, has more processing capability, and is more flexible than a multiplexer.
Controller or cluster controllers, link groups of terminals or other devices to a communications channels. The controller polls the status of each terminals and transfers data from a terminal to the host computer when necessary.
Multiplexers, concentrators and controllers are frequently used at termainals sites having heavy input and output requriements.

wireless transmission media

wireless transmission media used in communications include broadcast radio, microwaves, satellites & infrared. They are used when it is impractical & impossible to install cables. The following are the various types of unbounded transmission media.

1. Microwave:-

microwaves are radio waves that provides high speed signals transmission. It transmits signals from one microwaves station to another. Microwaves are limited to line of sights transmission which means that microwaves must be transmitted in a straight line. For e.g.- microwave transmission is used in wide open area such as deserts or lakes between building in a close geographical areas.

2. Satellite:-

A communication satellite is basically a microwave relay station placed in outer space. A satellite receives radio signals are a given frequency band changes their frequency & transmit them. The message signal is transmitted form the earth station through an up link through the satellite. It is amplified, translated to the downlink frequency in a transponders presents in the satellite and sent back to another earth station. The frequency transmitted from the ground station to the satellite is known as uplink & the frequency at which a satellite transmits amplified signals to the ground stations is known as down link frequency.

3. Infrared:-

It is a type of electro magnetic wave of large wave length & small frequency then visible light then its frequency is low. It is used in optical fiver communication, wireless LAN, mobiles & many other electronic devices.

4. Bluetooth:-

A proposed radio frequency specification that may portable devices may used for short range wireless communication is called Bluetooth. With Bluetooth devices such as laptop, handheld computers etc can have wireless communication with each other.

introduction networking

simply we can define networking is the process of establishing the links between two or more then two computers.
So that they can communicate with each other transfer data and progaramme and share their peripherals resources with each other. Hence, we can say that to establish a links between computers with the help of certain medium. Networking provides the following services to the users.
1. Personal communications:-
if we connect computers in network that we can send message from one computer to another easily.so, in networking it is easy to share the view of users around the staff member of any organization where they are connected to network.
2. Peripherals sharing: -
In the field of networking we can share the peripherals devise among various computers just by installing in one computer. For eg:- we can share one printer among the various computer if they are in network.
3. Data and programmer sharing:-
we can also share the total programme or data among the computers if they are in network. For eg:- we can install any programme in one machine but an be used by the different machines at a time if there is network facilities.
4. Easier backup:-
if the computer are in network then it is easy to make backup for recovery process. We can use one CD- drive to create backup of hundreds computer at once if they are in network.

Types of computer

The computers can be divided into four types according to their size:

• Micro Computer
• Mini Computer
• Main Frame Computer
• Super Computer

Micro Computer:

A microprocessor-based computer is known as microcomputer. It is also popularly known as the PC. It is very small, light, and portable. Viz.—Desktop Computers, Laptop, Palmtop, Pocket PC.

Mini Computer:

This category falls in between micro and mainframe computers. Generally, it can hold more than hundred terminals or microcomputers with one CPU performing different tasks at the same time.

Mainframe Computer:

These are the giant computers. They are suitable for large organizations as they have very high processing speed and accuracy. These computers can hold whole terminals with one CPU.

Super Computer:

These are the fastest, the most accurate, and the most expensive on the category of computerization. This category of computers has maximum processing capability. This type of computers performs space exploration, weather forecasting, e.t.c.