Networking and Telecommunication: Computer Science Class Ten

Class 10 Computer Lesson 1

Students of class ten are required to solve the given questions and submit the answer to the messenger group.

Networking and Telecommunication

Introduction

Data communication system

Components of data communication

Modes of Transmission

Communication media:

Guided Media

Unguided Media

Introduction

The word 'communication' means sending and receiving information between two or more persons. In 1870, Alexander Graham Bell invented telephone which revolutionized  the world and brought a drastic change in the long distance communication. The development of microcomputers in 1980's has has brought a new way of communication. The development of computer network system has made communication easier, faster and changed the world as 'global village'.

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Data Communication system

Telecommunication is a system of transmission of sound, images, texts or data in the form of electronic signals. Data communication refers to the exchange of data between a source and a receiver via form of transmission media such as a wire cable. Data communication is said to be local if communicating devices are in the same building or a similarly restricted geographical area.

Communication can be in one direction or both direction.  Radio, newspaper and television are the examples of one way communication while telephone and internet chat are examples of two way communication.

Components of data communication

In order to make communication and share data resource, the five basic components are required. They are data, sender, receiver, transmission medium and protocol

1. Data: 

Communication of data means a message or data will be transmitted from one device and will be received in the destination or target device. Thus the first component in a data communication network is data or message to that needs to be delivered and received. Data or message can be of various forms such as text, audio, video, image or combinations of these forms etc.

2. Sender: 

A data must has to be sent to a destination from a source. This source is called the sender. The device that sends the data to the destination or target is the Sender. It can be a computer, cell phone, video camera and so on.

3. Receiver: 

The destination of a transmitted data is the receiver which will receive the data. The device that receives the data that was sent by the Sender is the Receiver. A receiver can again be a computer, cell phone, video camera and so on.

4. Transmission medium: 

In data communication network, the transmission medium is the physical path for the data to travel to its destination after being sent by the Sender. Receiver receives the data at one end of this path and the sender sent from another end of the path. Transmission medium could be like twisted-pair cable, coaxial cable, fiber-optic cable etc.

5. Protocol: 

A protocol is nothing but a set of rules that applies on the full data communication procedure. This is like an agreement between the two devices to successfully communicate with each other. For example, how the data will be sent, how the data will be traveling, how to ensure that full data has received, how to handle errors in transmission etc. Both devices follow the same set of rules or protocol so that they understand each other.

Modes of Transmission

Transmission mode refers to the mechanism of transferring of data between two devices connected over a network. It is also called Communication Mode. These modes direct the direction of flow of information. There are three types of transmission modes. They are:

1. Simplex Mode
2. Half duplex Mode
3. Full duplex Mode

SIMPLEX Mode

In this type of transmission mode, data can be sent only in one direction i.e. communication is unidirectional. We cannot send a message back to the sender. Unidirectional communication is done in Simplex Systems where we just need to send a command/signal, and do not expect any response back.

Examples of simplex Mode are loudspeakers, television broadcasting, television and remote, keyboard and monitor etc.

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HALF DUPLEX Mode

Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time.

For example, on a local area network using a technology that has half-duplex transmission, one workstation can send data on the line and then immediately receive data on the line from the same direction in which data was just transmitted. Hence half-duplex transmission implies a bidirectional line (one that can carry data in both directions) but data can be sent in only one direction at a time.

Example of half duplex is a walkie- talkie in which message is sent one at a time but messages are sent in both the directions.

FULL DUPLEX Mode

In full duplex system we can send data in both the directions as it is bidirectional at the same time in other words, data can be sent in both directions simultaneously.

Example of Full Duplex is a Telephone Network in which there is communication between two persons by a telephone line, using which both can talk and listen at the same time.

Bandwidth of communication:

Bandwidth describes the maximum data communication rate of a network or internet connection. It measures how much data can be sent over a specific connection in a given amount of time. For example, a gigabit Ethernet connection has a bandwidth of 1,000 mbps (125 megabytes per second). An Internet connection via cable modem may provide 25 Mbps of bandwidth.

While bandwidth is used to describe network speeds, it does not measure how fast bits of data move from one location to another. Since data packets travel over electronic or fibre optic cables the speed of each bit transferred is negligible. Instead, bandwidth measures how much data can flow through a specific connection at one time.

Communication media:

A communication or transmission medium is a channel through which data or signals can be transmitted from one point to another. These signals are transmitted from one device to another through electromagnetic signals produced from devices in the form of radio waves, infrared light, ultraviolet rays, etc. The electromagnetic signals can be transmitted through vacuum, cables, fiber optic cables, etc. signals 

Types of Transmission Media

In data communication terminology, a transmission medium is a physical path between the transmitter and the receiver i.e it is the channel through which data is sent from one place to another. Transmission Media is broadly classified into the following types:

1. Guided Media:
Guided media are Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.

There are 3 major types of Guided Media:

(i) Twisted Pair Cable –
It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types:

1. Unshielded Twisted Pair (UTP):
   This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications

1. Advantages:

   • Least expensive
   • Easy to install
   • High speed capacity

   Disadvantages:

   • Susceptible to external interference
   • Lower capacity and performance in comparison to STP
   • Short distance transmission due to attenuation
2. Shielded Twisted Pair (STP):
   This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.

   Advantages:

   • Better performance at a higher data rate in comparison to UTP
   • Eliminates crosstalk
   • Comparitively faster

   Disadvantages:

   • Comparitively difficult to install and manufacture
   • More expensive
   • Bulky

(ii) Coaxial Cable –
It has an outer plastic covering containing 2 parallel conductors each having a separate insulated protection cover. Coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.

Advantages:

• High Bandwidth
• Better noise Immunity
• Easy to install and expand
• Inexpensive

Disadvantages:

• Single cable failure can disrupt the entire network

(iii) Optical Fibre Cable –
It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for transmission of large volumes of data.

Advantages:

• Increased capacity and bandwidth
• Light weight
• Less signal attenuation
• Immunity to electromagnetic interference
• Resistance to corrosive materials

Disadvantages:

• Difficult to install and maintain
• High cost
• Fragile
• unidirectional, ie, will need another fibre, if we need bidirectional communication

2. Unguided Media:
It is also referred to as Wireless or Unbounded transmission media.No physical medium is required for the transmission of electromagnetic signals.

Features:

• Signal is broadcasted through air
• Less Secure
• Used for larger distances

There are 3 major types of Unguided Media:

(i) Radiowaves –
These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and cordless phones use Radiowaves for transmission.

Further Categorized as (i) Terrestrial and (ii) Satellite.

(ii) Microwaves –
It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz. These are majorly used for mobile phone communication and television distribution.

(iii) Infrared –
Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz – 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.