history of telecommunication from telegraph to telephone
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OPTICAL TELEGRAPH
Early Forms of Long Distance Communication
Mankind has attempted to transmit long distance
communication since the advent o its technolog!"
Earlier telecommunications protot!pes resem#led
modern technological developments" In act$ the earliest
orms %ere the greatest achievements or the pioneers
o the time" &ome o the earliest orms o long distancecommunication included smoke signals$ %hich %ere
transmitted via signal to%ers across the %orld" &moke
signal to%ers used polished glass mirrors to rela!
messages along a chain o to%ers positioned in
strategical places" This orm o communication %as the
precursor to the light s!stem used during the
Revolutionar! 'ar" In a matter o decades$ people
across the glo#e kne% %hat these coded messages
meant" (or instance$ )one i #! land$ t%o i #! sea$*
#ecame a nota#le message across a distance" People
also used carrier pigeons to deliver messages across
long distances" The simplicit! o these communication
methods allo%ed or the development o sophisticated
tools used in modern telecommunication"
Centuries o slo% long+distance communications came
to an end %ith the arrival o the telegraph" Most histor!
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#ooks start this chapter %ith the appearance o the
electrical telegraph$ mid%a! the nineteenth centur!"
Ho%ever$ the! skip an important intermediate step" (it!
!ears earlier ,in -./-0 the (renchman Claude Chappe
developed the optical telegraph" Thanks to this
technolog!$ messages could #e transerred ver! 1uickl!
over long distances$ %ithout the need or postmen$
horses$ %ires or electricit!"
I2TRO34CTIO25
6 A#out Optical telegraph"
6 A#out morse telegraph"
6 Ho% the invention o #atter! and electromagnetism
changed the %orld"6 This led the initial developments o telegraph"
HI&TOR75
6 8er! irst drums and ire #eacons %ere used in
order to transer the inormation"
6 This is earl! kind o communication"
6 Later animals are used or an inormation carrier
such as horses$pigeons"
6 Later$optical telegraphs %ere invented until then
horses are the high speed carriers"
CHAI2 O( TO'ER&5
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The optical telegraph net%ork consisted o a chain o
to%ers$ each placed 9 to :; kilometres apart rom each
other" On each o these to%ers a %ooden semaphore
and t%o telescopes %ere mounted ,the telescope %as
invented in -t he used the telescope to look at the succeeding
to%er in the chain$ to control i the ne>t telegrapher hadcopied the s!m#ol correctl!" In this %a!$ messages %ere
signed through s!m#ol #! s!m#ol rom to%er to to%er"
The semaphore %as operated #! t%o levers" A
telegrapher could reach a speed o - to ? s!m#ols per
minute"
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(42CTIO2I2G5
6 Claude and chappe invented the optical telegraph
%hich %as also kno%n as mechanical telegraph"
6 This consists o : arms and a shat"
6 'here shat is kno%n as regulator and arms are
kno%n as indicators"
6 Later improvements increased the arms num#er to
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6 This does not re1uire an! electrical signals as input
#ut the operation is mainl! #! movement o lever
%hich is connected to arms and shat"
6 The signals that are send are received #! o#serving
through telescope"
6 These are mounted on top o to%ers"so that the!
can provide #est line o sight"
I2&I3E A23 O4T&I3E O( (RA2CE5
6 8er! irst line %as #uilt in rance #et%een paris and
lille"
6 In #et%een these : there %ere -9 stations"
6 Each station can receive ? letters in ?
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6 It is e>pensive,no o stations0"
6 It re1uires man po%er"
6 It re1uires line o sight"
6 'hether conditions should #e considered$%e canBt
see in dark"
CO2CL4&IO25
6 Here$i e>plained a#out histor! o telegraphs"
6 Mainl! optical telegraphs %hich gives an idea to the
electrical telegraphs to have lines and to use TD
and RD"
6 Also due to coding i"e #! using certain codes %e
have developed the semaphore"
6 This gave an idea to morse to develop morse code"
6 &o i conclude #! sa!ing that optical telegraph
provides root strength to communication"
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This igure indicates shat and regulator o optical
telegrap$ consists o : arms"
3eveloped version o optical telegarph consisted o <
arms to send more inormation"The optical telegraph
net%ork %as solel! used or militar! and national
communications$ individuals did not have access to it
although it %as used or transmitting %inning lotter!num#ers and stock market data"
The optical telegraph disappeared as ast as it came"
This happened %ith the arrival o the electrical telegraph$
it! !ears later" The last optical line in (rance %as
stopped in -F9?$ in &%eden the technolog! %as used up
to -FF;" The electrical telegraph %as not hindered #!
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mist$ %ind$ heav! rainall or lo% hanging clouds$ and it
could also #e used at night"
ELECTRICAL TELEGRAPH
The telegraph %as the irst rom o communication
that could #e sent rom a great distance and %as a
landmark in human histor!" (or the irst time man could
communicate %ith another rom a great distance
changing ever!thing rom ho% %ars %ere ought to ho%people dated and ell in love" ItBs creation$ along %ith the
steam engine$ %as one o the ke! inventions to the
industrial age" Letters took hours$ da!$ and even months
to arrive at their destination making most inormation
irrelevant" Ho%ever$ %ith the advent o the telegraph$
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messages %ere transmitted instantaneousl!$ and as it
#ecame ever more eicient the telegraph %as a#le to
rela! more comple> messages arther and arther till it
connected people rom around the %orld #! pressing a
e% #uttons"
3eveloped in the -F?;s and -F=;s #! Samuel Morse
,-./-+-F.:0 and other inventors$ the telegraph
revolutionied long+distance communication" It %orked
#! transmitting electrical signals over a %ire laid
#et%een stations"
The irst telegram in the 4nited &tates %as sent #!
Morse on 11 January 1838$ across t%o miles ,? km0 o
%ire at &peed%ell Iron%orks near Morristo%n$ 2e%erse!$ although it %as onl! later$ in 18$ that he sent
the message 'HAT HATH GO3 'RO4GHT rom the
Capitol in 'ashington to the old Mt" Clare 3epot in
@altimore"
Ater the invention o optical telegraph several
developments took place in the communication
ield"chemical telegraph #! using electrol!sis
process$electro magnetic telegraph i"e #! using
magnetic needles several developments %ere made"@ut
it %as the morse telegraph %hich had changed the
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%orld"It %as the ver! irst international communication
s!stem"
The mechanism o electrical telegraph re1uires not more
than a ke!$#atter!$ca#les$paper$line o poles #%
transmission and reception"%hen press the ke!$circuit is
closed and the %ire is connected to #atter! and negative
is grounded"%hen ke! is closed current is passed
through the %ire to the coil connected to a rod %hich is
electro+magnetic and that attracts the armature"%here
the other end o armature is having a spring"The
armature on the coil side is having a marker pointing on
a paper,dots and dashes0"
'here the received signals on the paper are in the orm
o dots and dashes"This is kno%n as morse code"Eachletter and alpha#et is indicated %ith com#ination o dots
and dashes"And here signal is to #e listened %hen it
makes sound and moreover itBs is hard to understand
and produce it astl!"
This morse code is even used in da! to da! modern
lie"ItBs used %hen there is no availa#ilit! o modern
communication due to #ad climatic conditions"Hams
radio is used to communicate at that situations %here it
onl! re1uires a #atter! and morse code to code"%here it
is 9; times more aster than the modern voice message
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communication"This is useul or soldiers at their remote
%ork places to send the signals"It is used in arm! to
communicate or to send private inormation
%isel!"Ho%ever it had changed and #ought the %orld a
head #ut signal sensing comple>it! is more and %ith the
ne% developments it had #een let a side"
The electric telegraph transormed ho% %ars %ere
ought and %on and ho% Journalists and ne%spapers
conducted #usiness" Rather than taking %eeks to #e
delivered #! horse+and+carriage mail carts$ pieces o
ne%s could #e e>changed #et%een telegraph stations
almost instantl!" The telegraph also had a proound
economic eect$ allo%ing mone! to #e )%ired* across
great distances"
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TELEPHO2E Ale>ander Graham @ell ,-F=.+-/::0$ the &cottish+#orn
American scientist #est kno%n as the inventor o the
telephone$ %orked at a school or the dea %hile
attempting to invent a machine that %ould transmitsound #! electricit!" @ell %as granted the irst oicial
patent or his telephone in March -F.
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rest o his lie$ and used his success and %ealth to
esta#lish various research centers nation%ide"
@ell o%es his immortalit! to his having #een the irst to
design and patent a practical device or transmitting the
human voice #! means o an electric current" @ut @ell
al%a!s descri#ed himsel simpl! as a )teacher o the
dea$* and his contri#utions in that ield %ere o the irst
order"
@ell$ %ho %as #orn in Edin#urgh$ &cotland$ %as
educated there and at the 4niversit! o London" He also
studied under his grandather$ Ale>ander @ell$ a noted
speech teacher" He taught elocution$ assisted his ather$
also a speech teacher and noted phonetician$ and
taught at a school or the dea in England$ using hisatherBs methods" In -F.;$ @ell immigrated %ith his
parents to Canada"
T%o !ears later he esta#lished a school or the dea in
@oston$ Massachusetts$ and the ollo%ing !ear #ecame
a proessor in speech and vocal ph!siolog! at @oston
4niversit!" 'hile teaching he e>perimented %ith a
means o transmitting several telegraph messages
simultaneousl! over a single %ire and also %ith various
devices to help the dea learn to speak$ including a
means o graphicall! recording sound %aves"
http://www.history.com/topics/us-states/massachusettshttp://www.history.com/topics/us-states/massachusetts
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In -F.= the essential idea o the telephone ormed
in his mind" As he later e>plained it$ )I I could make a
current o electricit! var! in intensit! precisel! as the air
varies in densit! during the production o sound$ I should
#e a#le to transmit speech telegraphicall!"* T%o !ears
later he applied or a patent$ %hich %as granted on
March .$ -F.
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TELEPHO2E PART&56 HA23&ET
6 MO4THPIECE
6 MICROPHO2E
6 LO43&PEAER
LetNs think a#out a t!pical phone handset" At the top$
thereNs a loudspeaker !ou press against !our ear" At the
#ottom$ thereNs a microphone !ou put near !our mouth"
Coming out o the handset$ %rapped inside a single
thick$ coiled ca#le$ are t%o pairs o copper %ires" One
pair is an output5 it takes outgoing electrical signals rom
the microphone to the telephone s!stem the other pair
is an input5 it takes incoming signals rom the telephone
s!stem to the loudspeaker"The loudspeaker and
microphone %ork in similar #ut opposite %a!s" The
http://www.explainthatstuff.com/microphones.htmlhttp://www.explainthatstuff.com/microphones.html
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microphone contains a le>i#le piece o plastic called a
diaphragm %ith an iron coil attached to it and a magnet
near#!" 'hen !ou speak into the mouthpiece$ the sound
energ! in !our voice makes the diaphragm vi#rate$
moving the coil nearer to or urther rom the magnet"
This generates an electric current in the coil that
corresponds to the sound o !our voice5 i !ou talk loud$
a #ig current is generated i !ou talk sotl!$ the current is
smaller" 7ou can think o a microphone as an energ!
converting device5 it turns the sound energ! in !ourvoice into electrical energ!" &omething that converts
energ! rom one orm to another is called a transducer"
The loudspeaker in a phone %orks in the opposite %a!5
it takes an incoming electrical current and uses
magnetism to convert the electrical energ! #ack into
sound energ! !ou can hear" In some phones$ theloudspeaker and microphone units are virtuall! identical$
Just %ired up in opposite %a!s"
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!o" lou#s$eakers turn electricity into soun#
'hen things shake a#out$ or vi#rate$ the! make the
sounds %e can hear in the %orld around us" &ound is
invisi#le most o the time$ #ut sometimes !ou can
actuall! see it I !ou thump a kettle+drum %ith a stick$
!ou can see the tight drum skin moving up and do%nver! 1uickl! or some time ater%ardKpumping sound
%aves into the air" Loudspeakers %ork in a similar %a!"
At the ront o a loudspeaker$ there is a a#ric$ plastic$
paper $ or light%eight metal cone ,sometimes called a
#ia$hragm0 not unlike a drum skin ,colored gra! in our
picture0" The outer part o the cone is astened to the
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outer part o the loudspeakerNs circular metal rim" The
inner part is i>ed to an iron coil ,sometimes called the
%oice coil$ colored orange in the diagram0 that sits Just
in ront o a permanent magnet ,sometimes called the
fiel# magnet$ and colored !ello%0" 'hen !ou hook up
the loudspeaker to a stereo$ electrical signals eed
through the speaker ca#les ,red0 into the coil" This turns
the coil into a temporar! magnet or electromagnet" As
the electricit! lo%s #ack and orth in the ca#les$ the
electromagnet either attracts or repels the permanentmagnet" This moves the coil #ack and or%ard$ pulling
and pushing the loudspeaker cone" Like a drum skin
vi#rating #ack and orth$ the moving cone pumps sounds
out into the air"
!o" micro$hones "ork
Ho% does a microphone turn sound energ! intoelectrical energ! Like this5
-" 'hen !ou speak$ soun# "a%es created #! !our
voice carr! energ! to%ard the microphone"
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Remem#er that sound %e can hear is energ!
carried #! vi#rations in the air"
:" Inside the microphone$ the #ia$hragm ,much
smaller than !ouNd ind in a loudspeaker and usuall!
made o ver! thin plastic0 moves #ack and orth
%hen the sound %aves hit it"
?" The coil$ attached to the diaphragm$ moves #ack
and orth as %ell"
=" The $ermanent magnet produces a magnetic ield
that cuts through the coil" As the coil moves #ackand orth through the magnetic ield$ an electric
current lo%s through it"
9" The electric current lo%s out rom the microphone
to an ampliier or sound recording device" He!
presto$ !ouNve converted !our original sound into
electricit! @! using this current to drive soundrecording e1uipment$ !ou can eectivel! store the
sound orever more" Or !ou could ampli! ,#oost the
sie o0 the current and then eed it into a
loudspeaker$ turning the electricit! #ack into much
louder sound" ThatNs ho% PA ,personal address0
s!stems$ electric guitar ampliiers$ and rock concertampliiers %ork"
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converted rom one orm to another and getting #ack our
original voice signal"
ROTAR7 8& 3AIL TO2E E7PA35
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These igures indicates the internal and e>ternal vie% o rotar! ke!pad"
&one Dialing %s 'ulse Dialing
Tone and pulse dialing are t%o %a!s o communicating%ith the central telephone rela! to indicate the telephone
num#er that !ou %ish to call" Pulse dialing indicates
each digit in the phone num#er #! a series o clicks that
corresponds onl! to that digit" It %ould then need a short
pause in order to clearl! identi! one digit rom the ne>t"
Tone dialing$ also called as 3ual Tone Multi (re1uenc!$uses dierent tones to indicate a dierent num#er"
Instead o sending multiple signals or each digit$ it
%ould onl! need to send one or each"
(or most cases$ the most discriminating part #et%een
phone sets that use pulse or tone dialing is the
mechanism used to dial the num#er" Tone dialing
handsets use a numeric ke!pad %here !ou simpl! push
each digit" Although there are some versions o pulse
dialing phones %ith numeric ke!pads$ the most
prevalent models %ere those e1uipped %ith rotar! dials"
This dierence #et%een the t%o has huge implications
%ith the ease o use" 3ialing a num#er %ith a rotar! dial
takes a lot longer since !ou %ould need to %ait or thedial to return in its resting position #eore !ou can dial
the ne>t digit" This is not an issue %ith tone dialing
phones !ou can dial as 1uickl! as !ou can or %ant
%ithout causing an! pro#lem"
3ue to the advantages o tone dialing$ it has no%
#ecome the standard or telephone companies all over
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the %orld" 7ou %ould #e hard pressed to ind an area
that still uses pulse dialing" 3espite this$ most telephone
s!stems that uses tone dialing are also a#le to
recognie and %ork %ith pulse dialing" &ome handsetsare also manuactured to support #oth pulse and tone
dialing"
The 3TM( telephone ke!pad is laid out in a =Q= matri>
o push #uttons in %hich each ro% represents the low
re1uenc! component and each column represents thehigh re1uenc! component o the 3TM( signal" Pressing
a ke! sends a com#ination o the ro% and column
re1uencies"
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