BY SMRITI MAMGAIN
Telecommunication is the transmission of signs,signals,messages,writing,images and sounds or intelligence of any nature by wire,radio,optical or other electromagnetic system.Telecommunication occurs when the exchange of information between communication participants include the use of technology.It is transmitted either electrically over physical media such as cables or via electromagnetic radiation.such transmission paths are often divided into communication channels which afford the advantage of multiplexing.The term is often used in its plural form,telecommunication,because it involves many different technology.
Telecommunication technology may divided into wired and wireless method.A basic telecommunication system consist of three main parts:
- A transmitter,that takes information and converts it to h signal.
- A transmission medium,also called the physical channel that carries the signal.
- A receiver that takes the signal from the channel and converts it back into usable information for the recipient.
Telecommunication over fixed lines is called point to point communication because it is between one transmitter and one receiver.Telecommunication through radio broadcast is called broadcast communication because it is between one powerfull transmitter and numerous low power but sensitive radio receiver.
A telecommunication network is a collection of transmitter,receivers and communication channels that send messages to one another.Some digital communication networks contain one or more routers that work together to transmit information to the correct user.An analog communication network consist of one or more switches that establish a connection between two or more user.
The term channel has two different meanings.In one meaning ,a channel is the physical medium that carries a signal between the transmitter and the receiver.Examples of this include the atmosphere for sound communication,glass optical fibres for some kinds of optical communication,coaxial cables for communication by way of the voltages and electric currents in them,and free space for communication using visible light,infrared waves,uv light and radiowaves.
The shaping of a signal to convey information is known is modulation.Modulation can be used to represent a digital message as an analog waveform.Modulation can also be used to transmit the information of low frequency analog signal at higher frequencies.This is helpful because low frequency analog signals cannot be effectively transmitted over free space.Hence the information from a low frequency analog signals must be impressed into a higher frequency signal before transmission.There are several different modulation schemes available to achieve this[two of the most basic being aptitude modulation and frequency modulation.
In a telephone network,the caller is connected to the person they want to talk by switches at various telephone exchanges.Te switches form an electrical connection between the two user and the setting of these switches is determined electronically when the caller dials the number.Once the connection is made,the callers voice is transformed to an electrical signal using a small microphone in the callers handset.This electrical signal is then sent through the network to the user at the other end where it is transformed back into sound by a small speaker in that persons handset.
The landline telephones is most residential homes are analog-that is,the speakers voice directly determines the signals voltage.Although shot distance calls may be handled from end to end as analog signals,increasingly telephone service providers are transparently converting the signals to digital signals for transmission.
Radio and television
In a broadcast system,the central high powered broadcast tower transmits a high frequency electromagnetic waves to numerous low power receiver.The high frequency waves sent by the tower is modulated with a signal containing visual or audio information.The broadcast system can be either analog or digital.The broadcast media industry is at a critical turning point in its development,wth many countries moving from analog to digital broadcast.This move is made possible by the production of cheaper,faster and more capable integrated circuits.The chief advantage of digital broadcast is that they prevent a no. of complaints common to traditional analog braoadcasts.For television,this includes the elimination of problems such as snowy pictures,ghosting and other distortion.These occur because of the nature of analog transmission,which means that perturbations due to noise will be evident in the final output.
The internet is a worldwide network of computers and computer networks that communicate with each other using the internet protocol.Any computer on the internet has a unique IP address that can be used by other computer to route information to it.Hence any computer on the internet can send a message to any other computer by using its IP address.This message carries with them the originating computers IP address allowing for two way communication.The internet is thus an exchange of messages between computers.The internet works in part because of protocol that govern how the computers and routers communicate to each other.The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more or less independently of other protocols.This allows lower level of protocol to be customized fo the network situation while not changing the way higher level of protocol operate.
Local area network (LAN) and Wide area network (WAN)
Despite the growth of the internet,the characterstics of local area network-computer network that do not extend beyond a few kilometers-remain distinct.This is because networks on the scale do not require all the features associated with larger networks and are often more cost effective and efficient without them.When they are not connected with the internet,they also have the advantages of privacy and security.However,purposefully lacking a direct connection to the internet does not provide assured protection from hackers,military forces,or economic power.
Wide area network are private computers that may extend for thousand of kilometers.Some of their advantage include privacy and security.Prime users of private LAN and WAN include armed forces and intelligence agencies that must keep their information secure and secret.