Information and Communication Technology (Study Material)




Information and Communication Technology : General abbreviations and terminology.

Basics of Internet, Intranet, E-mail, Audio and Video-conferencing.

Digital initiatives in higher education.

ICT and Governance

Some important Abbreviations and terms related to Information and Communication Technology

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ICT Glossary – Some Important Terms Related To ICT

Meaning   of  ICT

Information Technology (IT) as the name suggests deals with the technology  that is used to handle information. It concerns with the storage, communication   and processing  of information.  The IT has become a key to the survival  of the business  houses.  Information  Technology in its fully convergent form, encompassing  various  modes  of information  delivery, such as printed  media, radio and television, computer  and  internet,  into one integrated   environment   provides  an unique  opportunity   to touch the lives of everyone, overcoming  earlier divisions. Computer  is one of the major components  in Information Technology. Its application  has penetrated   every  sphere  of existence  of modem   man: Airlines, railways, weather  forecast medical  diagnosis,  entertainment,   banking …. the list is endless.

India’s capabilities  in the field of Information  Technology  provide  not only an opportunity   to participate vigorously and effectively in a globalizing world, but also to use it as a major vehicle for all- round socio-economic development   of the country. To ensure  the benefits  of an IT-based knowledge   economy  India  needs  to adopt  the two  fold strategies:(i) a number  of steps to ensure that the Indian IT industry  grows at a fast pace in consonance with international  trends: and (ii) to intend  to take all possible measures  to ensure  that the benefits of his technology are meaningfully  felt by the common people and reach to even in the remotest  parts of the country.

Data Transmission Media

The most basic hardware   required  for communication   is the media  through  which  data is transferred. There are several types of media, and the choice of the right media  depends  on many  factors such as cost of transmission   media,  efficiency of data  transmission   and  the transfer  rate. We will describe some of these transmission  media.

1. Twisted Pair Cable

The most common  form of wiring  in data communication   application  is the twisted  pair cable. It consists of a pair of insulated  conductors (copper wires)  that are twisted  together. It is also called  unshielded   twisted-pair   (UTP)  cable  because  other  than  the  plastic  insulation   around  the  two  individual bunches  of copper  wires, nothing  else shields  it from outside  interference.The advantage  of a twisted  pair cable    is to provide better immunity  from spurious  noise signals. Twisted pair cable is used for communication  upto a distance  from 1 km and can achieve transfer  rates of 1-2 megabytes  per second. But, as the speed increased the maximum  transmission distance is reduced, and may require repeaters. Twisted pair cable is widely  used  in telephone  networks  and are increasingly  being used  for data.

2. Coaxial Cable

Coaxial cables are groups of specially wrapped and insulated wire lines capable of transmitting data at high rates. They consist of a central copper wire surrounded by a PVC insulation over which there is a sleeve of copper mesh. Te copper mesh sleeve is shielded again by an outer shield of thick PVC material. Larger the cable diameter, lower is the transmission  loss, and higher transfer speeds  can be achieved. A coaxial cable can be used  over a distance  of about  1 Km. and can achieve transfer  rate of upto 100 megabytes  per second.

A coaxial cable is of two types-a 75 ohm cable which is used by the cable TV operators  and the 50 ohm cable which  is used  in high speed broadband   network  and are low loss cables. They are also used by telephone companies to transmit data. Telephone companies often package several coaxial cables into a very large cable, which can handle over 40,000 telephone calls simultaneously.

3. Optical Fibre Cables

An Optical Fibre Cable carries signals in the form of fluctuating  light in a glass or plastic fibre. An optical fibre cable consists of a glass or plastic core surrounded   by a closing made  of similar material but with a lower refractive index. The core transmits  the light while the change in refractive index between  the core and the cladding  causes total internal  reflection, thus minimizing  the loss of light from fibre. A light waves gave a much wider band width  then the electric signal and are immune  from elettromagnetic  interferences,  this leads to high data transfer  rates of about  1000 megabytes  per second and can be used  for long and medium distance  transmission   links.

4. Radio, Microwave     and   Satellite    Channels

Radio, microwave  and satellite channels  are use electromagnetic     propagation   in open space. The advantage  of these channels  lie in their capability  to cover large geographical  areas and being inexpensive  then the wired  installation.  The demarcation  between  radio,  microwave  and satellite channels lies in the frequencies  in which they operate. Frequencies  below 100 MHz are radio frequencies and higher are the microwave  frequencies.  Radio frequency transmission may be below 30 MH and  thus  the techniques   of transmission   are different.  Owing  to the characteristics   of the ionosphere, frequencies  below 30 MHz are reflected back towards  the surface of the earth. Above 30 MHz propagation is one line-of-sight paths. Antennas  are placed in between  the line of sight paths  to increase the distance. Radio frequencies  are prone to attenuations  and, thus, they require repeats  along the path to enhance  the signal. Radio frequencies  can achieve data transfer  rates of 100 Kbps to 400 Kbps.

Microwave systems use very high frequency radio signals to transmit data through space. However, at microwave frequencies, electromagnetic waves cannot bend or pass obstacles like tall buildings or hills. Hence, transmitter and receiver of a microwave system , mounted on very high towers, should be in line of sight. This may not be possible for very long distance transmission. Moreover, signals become weaker after travelling a certain distance and require power amplification. To overcome problems of line of sight and power amplification of weak signals, microwave systems use repeaters at intervals of about 25 km to 30 kms in between transmitting and receiving stations. Microwave systems have speed of about 16 giga bps. They can support about 250,000 voice channels simultaneously.

Main problem with microwave communication is that curvature of earth, mountains and other structures often block the line of sight. This problem is overcome by using satellites. Communication satellites are microwave relay stations placed in outer space. Each satellite can receive and retransmit signals to slightly less than half the earth’s surface. Therefore,at least three satellites are needed in geosynchronous orbit to provide data transmission service worldwide. The INSAT series of Indian satellites are positioned in outer space in a manner to be accessible from any place in India.    In satellite communication microwave signal at 6 GHz or 14 GHz is transmitted from a transmitter on earth to a satellite positioned in space. By the time signal reaches the satellite, it becomes weak due to 36,000 kms travel. A transponder, mounted on the  satellite, amplifies the weak signal and transmits it back to earth at a frequency of $ GHz or 11 GHz.  A transponder   can  support  typically   1200 voice  channels   each  of 4800  bps,  or 400 digital  channels  each  of 64 Kbps  (Kilo  bits  per  second).  A satellite  has  many  transponders.   Therefore,   a single  satellite  has  enormous  data communication   capability.

Use  of  4  GHz  to  6  GHz  band  of  frequencies   for  transmission   and  retransmission    of  microwave   signals   in a satellite  communication   system  is called  C-band  transmission,   and use of 11 GHz  to  14 GHz band of frequencies is called    Ku-band transmission.

To enable  a large  number  of users  to benefit  from  satellite  communication,    it was  realized  that  size  and cost  of receive-transmit   earth  stations  has to be considerably  reduced,  so that one can easily  install a private  earth  station. To  meet  this  requirement,   smaller  dish  antennas,  having  lower  power  transmitters   and  receivers,   were  built  for installation   at  users’   sites.  These   dish  antenna   systems  are  popularly   known   as  VSATs   (Very  Small  Aperture Terminals ).

5. Digital and   Analog    Transmission

Analog transmission has dominated communication for the last few decades. Analaog signals carry data as continuous wave form. In analog transmission, normally continuously varying voltage is used for such transmission. Telephone line is a good example of analog transmission media. Analog transmission is generally used for the transmission of voice signals or TV signals. Amplitude of an analog signal is measured n volts and its frequency (f) in hertz (Hz). When analog signals are transmitted over long distances, they become weak and distorted as they travel. Hence, amplifiers are used at periodic intervals along analog communication lines between modems to amplify weak analog signals.In terms of voltage, voice can be represented as follows:

Digital Transmission

Digital signal is a sequence of voltage pulses represented in binary form. When digital signals are transmitted over long distances, repeaters are used at periodic intervals along digital communication lines to strengthen weak digital signals.

Computer generated data is digital, whereas telephone lines used for data communication in computer networks usually carry analog signals. Digital transmission of digital data is preferred to analog transmission of digital data due to its lower cost, high transmission speed and lower error rate.


A special device called modem (modulator/demodulator) is used to carry out the process of modulation and demodulation. Hence when an analog facility is used for data communication between two digital devices, two modems are required, one near each device. Digital signal generated at sender computer’s end is converted to analog form by modulator of the modem placed near it. The analog signal is transmitted through telephone line and is converted to digital form by demodulator of the modem placed near receiver computer. The receiver computer processes the data, and then the modem near it modulated the processed data to analog form. The analaog data is returned via telephone line to the sender computer end, where analog signals are demodulated to digital form first by the modem there, and then digital data is passed on to the sender computer.  Higher the modem’s transmission speed, better it is because it can communicated faster. Transmission speeds of earlier modems were 300, 1200 or 2400 bps. Modems available now can operate at 9600, 14400 or 28800 bps. Modems are of two kinds:

1. Internal

2. External

3. Internal modem is an optional add- on circuit board that plugs into one of the computer’s expansion slots. It gets its power from computer’s expansion bus. It is manufactured and supplied by computer manufacturers.

4. External Modem is a separate box containing circuitry and logic to modulate data signals. It has its own power supply, in/oof switch, and front panel LCDs to indicate its status. External modems are slightly more expensive than internal modems. An external modem is connected to a computer via serial port.

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