telephone (gnv64)

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  • 8/9/2019 Telephone (Gnv64)



  • 8/9/2019 Telephone (Gnv64)


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  • 8/9/2019 Telephone (Gnv64)





    1875- The first telephone instrument madeby Alexander Graham Bel l in 1875


    1879 1880 1880 1905 The telephone t-today


    The candlesticktelephone of 1905

    The Gower-Bell telephone oft he ear ly 18 80 's with tw ol istening tubes

    This device required the user speak into the box with thereceiver to his ear (1880)I

    An Edison receiver (1879)I

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    R. Watson, come here, I want to seeyou," shouted an angry Bell.Watson jumped out of his chair. There wasno one in the room. Yet he'd heard a voice.It was a familiar voice and it was loud andclear. Then suddenly it hit him. Thetelephone. It had come alive at last. Themiracle had happened. .

    Watson rushed to Bell's room, breathlesswith joy. "I could hear you. It works," he said.That was March 10, 1876. More than ahundred years ago.From ship to shore; from air to land; fromcar to car; from just about anywhere toanywhere today you can speak to someoneby just dialling a number. In fact, you havethe world at your finger-tips. And whenAstronaut Rakesh Sharma calls up Mrs. IndiraGandhi from space you just take it in yourstride. So dramatic has been the developmentof the telephone. And only forty years beforethe telephone was invented, man was patting

    himself on his back for having perfected themethods of communication.That was when the electric telegraph wasused. It was in 1838 that the American,Samuel Morse, patented his single wiretelegraph. His design used the famous Morsecode in which combinations of short and longsignals - dots and dashes - indicate letters.Messages were sent at up to ten words aminute with a hand-operated key and werereceived as marks made by a pen on a papertape. These signals had to be decoded andwritten out by hand.

    In 1855 Professor David Hughes inventeda printing telegraph. The operator sentmessages from a keyboard, each key ofwhich represented a letter. The machineturned the letters into electric signalsautomatically and, at the other end, anothermachine printed the message.These were major breakthroughs in thefield of communication, but still not the sameas 'talking' to someone, and nowhere nearhaving a cosy chat with someone.

  • 8/9/2019 Telephone (Gnv64)


    It was at this time that Alexander GrahamBell, the young professor of speech, beganhis experiments with electricity. Oftenhe would visit the mills and factories locatednear his house and observe how themachines were operated. Once he called onCharles Wheatstone, the inventor of the. magnetic needle telegraph. So impressedwas he by this mail that he determined tofollow in his footsteps.Bell was keen to develop a telegraphsystem that would allow multiple transmissionof messages at once. He felt that this couldbe achieved by transmitting each messageon a separate, specially tuned steel strip, orreed. Each reed would vibrate a differentnumber of times per second and so producea different musical note.It was while one such experiment wasbeing carried out, on June 2, 1875, that areceiving reed, which was being watched

    closely by his assistant, Thomas Watson, inanother room, failed to vibrate. Watsonthought the reed was stuck and pulled at it.When he did that. a similar receiving reedvibrated in Bell's room."What's this!" said Bell astonished, butrealized almost immediately that he had hitupon something great. He had discoveredthat a tiny electric current caused by onevibrating reed was powerful enough to causeanother reed to vibrate audibly. He alsorealized that instead of a single note the reedhad reproduced several notes. Humanspeech, as Bell knew only too well, is alsomade up of a mixture of sounds of differentfrequencies and Bell believed that he coulduse this system to transmit the human voice.Lo and behold, a month later, Bell produceda pair of simple telephones.Bell had made a deep study on sounds ashe had always wanted to help deaf and dumbchildren. He, therefore, knew that a stretchedmembrane would be more suitable for sound

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    . Bell demonstratingthe first telephone


  • 8/9/2019 Telephone (Gnv64)



    Number, pleaseAs news spread, a keener interest wascreated in the telephone, though it wasrestricted to small areas until the 1890's.Individual subscribers were connected toeach other by exchanges that were controlledby operators.When somebody wished to make a call all

    he did was lift the receiver and wait for theoperator's response."Number, please," the operator would sayand connect you to the number you wanted.In fact, so personal was everything thosedays that on some exchanges all you did

    . ...

    .reproduction than a reed. He finally decidedto use an iron diaphragm. On March 10, 1876,when he accidently discovered that his phoneworked, he was delirious with joy.It was the first time in the world that peoplecould talk to each other over long distancesand feel that they had almost met the person.After all there can be no substitute for ahuman voice.Bell was keen to promote the idea of thisnew device and travelled extensively in theUnitedStates and Europe to spread the word.He even demonstrated how one could talk tosomeone under water.But most people pooh-poohed the idea. InLondon, a post office official said it wouldnever catch on because there were sufficientmessenger boys.

    Finally on January 24, 1878, Bell carriedout a demonstration for Queen Victoria atOsborne House, on the Isle of Wight. Soimpressed was the Queen that she askedBell to supply her with telephonesImmediately.

  • 8/9/2019 Telephone (Gnv64)


    An 1879 hand-operated switchboardwas lift the receiver and ask for the personyou wished to talk to. Only one had to shoutin order to be understood by the other person.

    Early models resembled a box camera witha round projection at one end. This servedas the transmitter and receiver. So anyonemaking a call had to be extremely carefulwhile moving his ear and mouth. Bruised lipsand ears were not an uncommon sight. Infact, one model carried the notice: "Do notlisten with your mouth and talk with your ear!"

    Do Not L i ~ i f NWith YWRMouth A ~ 1ciJkwith

    OUI" Bo.Y'!

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    As Bell's transmitters had poor sensitivity,calls were limited to a few miles. It was atthis time that Thomas Alva Edison, thefamous American inventor, stepped in.Edison was the next best thing thathappened to the telephone. He produced atelephone with a separate mouthpiece anda much superior transmitter with a carboncomponent. When spoken into,it changed thesound of the voice into a varying electricalsignal which was converted back into speechby the ear-piece at the other end.By the beginning of the 1900's, thetelephone had grown in popularity, especiallyin the United States. Some exchanges wereso large that there were long lines ofoperators seated at switch boards made upof hundreds of plugs and sockets.

    India, believe it or not, was one of the firstcountries in the world to have a telephoneexchange. And Calcutta was where it allstarted.In 1881, barely five years after Bell madehis discovery, a 50-line exchange was set upin Calcutta. Then came the automatictelephone exchange with 700 lines, whichwas established in Shimla in 1913. But it wasonly after 1951 that the Indian telephoneservice made rapid progress. SubscriberTrunk Dialling (STD), first introduced betweenKanpur and Lucknow in 1960, now operateson practically every route in India and manyoutside the country too.

    'Tele' literally means 'at a distance' and'phone' is an instrument using sound. Thus'telephone' would imply 'an instrument thatcarries sound from a distance.'

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    Today telephone users in most parts of theworld can dial 80% of the world's subscribersdirectly. Telephone 'hot-lines' keep worldleaders in contact with each other to avoidthe accidental outbreak of a nuclear war.Even on the battlefield it is now possible tolink soldiers to the international telephonenetwork and a person from the most isolatedoil platform in the sea can make callsthroughout the world.Your parents can hold internationalbusiness meetings by merely going to aclosed circuit television studio and talking toexecutives in similar studios in other countrieswhile the television pictures and the soundare being carried over the telephone network.The telephone network has also been ableto link computers in many countries to vastinformation networks. It can transmittelevision programmes such as the OlympicGames to more than a 100 countries. It can

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    be used to turn a television set into a terminalconnected to a computer, providing vastamounts of information through videotex.In the future this could form the basis ofan electronic mail service with people sendingprivate messages from one television set toanother via the telephone network. It wouldbe cheaper and much faster thanconventional post.With so much happening around us it ishard to believe that once upon a timemessages were sent by using a line ofbonfires on hill-tops, by beating drums ortying notes to carrier pigeons trainedto fly home quickly from a distance.

    Few of us realize how complex andingenious is the mechanism that is set inmotion the moment one dials a telephonenumber. How does your voice get car