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Unit 6

TELECOMMUNICATIONS

AIM: To recognize the English technical terms related to telecommunications and thedevelopment of this field;

OBJECTIVES: On successfully completing this unit the student should be able to:

- identify correctly the terms defining telecommunicationsdevices and systems;

- recognise the specific terms related to telegraph-, telephone-and broadcasting systems;

- characterise the operation principles of each branch oftelecommunications;

- identify the types of equipment used for transmitting andreceiving the various types of signals;

- describe the applications made possible by eachtelecommunications system;

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- assimilate at least 3 terms specific of sending, receiving, andconverting signals;

KEY TERMS:

electronic signal, optical signal, sender, recipient, telephone system, medium, radio wave, strandof glass fibre, point-to-point, point-to-multipoint, facsimile (fax) message, broadcast, telegraph,intercity message, transcontinental message, transoceanic message, electromagnetism,

prototype, decipher, switching technology, , long-distance telephone service, public

communications, Morse-code telegraph signal, wireless telegraphy, mass-communication

TELECOMMUNICATIONS6.1. IntroductionTelecommunications, devices and systems that transmit electronic or optical signals across longdistances! Telecommunications enables people around the "orld to contact one another, to accessinformation instantly, and to communicate from remote areas! Telecommunications usuallyinvolves a sender of information and one or more recipients lin#ed by a technology, such as atelephone system, that transmits information from one place to another! Telecommunicationsenables people to send and receive personal messages across to"n, bet"een countries, and to and

from outer space! $t also provides the #ey medium for delivering ne"s, data, information, andentertainment!Telecommunications devices convert different types of information, such as sound and video,into electronic or optical signals! Electronic signals typically travel along a medium such ascopper "ire or are carried over the air as radio "aves! Optical signals typically travel along amedium such as strands of glass fibres! %hen a signal reaches its destination, the device on thereceiving end converts the signal bac# into an understandable message, such as sound over atelephone, moving images on a television, or terms and pictures on a computer screen!

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Telecommunications messages can be sent in a variety of "ays and by a "ide range of devices!The messages can be sent from one sender to a single receiver &point-to-point' or from onesender to many receivers &point-to-multipoint'! (ersonal communications, such as a telephoneconversation bet"een t"o people or a facsimile &fa)' message, usually involve point-to-pointtransmission! (oint-to-multipoint telecommunications, often called broadcasts, provide the basis

for commercial radio and television programming!6.2. i!tor"*ommunicating over long distances has been a challenge throughout history! +oderntelecommunications began in the s "ith the discovery that electricity can be used to transmita signal! .or the first time, a signal could be sent faster than any other mode of transportation!The first practical telecommunications device to ma#e use of this discovery "as the telegraph!

6.2.1. T#$ T$%$&r'(# /eginning in the mid- s, the telegraph delivered the first intercity, transcontinental, and

transoceanic messages in the "orld! The telegraph revolutionized the "ay people communicated by providing messages faster than any other means provided at the time! 0merican art professor1amuel .! /! +orse pursued an interest in electromagnetism to create a practical electromagnetictelegraph in 32! +orse partnered "ith 0lfred ail and "as able to commercialize thetechnology "ith financial support from the 4!1! government! $n 53 +orse built ademonstration telegraph lin# bet"een %ashington, 6!*!, and /altimore, +aryland! On +ay 75,55, the net"or# "as inaugurated for commercial use "ith the message, 8%hat hath 9od

"rought 8Telegraph use quic#ly spread; the first transcontinental lin# "as completed in bet"een 1an.rancisco, *alifornia, and %ashington, 6!*!

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The first commercial telephone line "as installed in /oston, +assachusetts, in 22! Earlytelephones required direct connections to other telephones, but this problem "as solved "ithtelephone e)change s"itches, the first of "hich "as installed in >e" ?aven, *onnecticut, in2 ! 0 telephone e)change lin#ed telephones in a given area together, so a connection bet"een

the telephone and the e)change "as all that "as needed! Telephones "ere much more convenient

and personal than telegrams, and their use quic#ly spread! /y @ 3 telephone lines from >e"Aor# *ity to 1an .rancisco had been established, and by @3 radio signals could transmittelephone calls bet"een >e" Aor# and Bondon, England! Eventually, long-distance telephoneservice in the 4nited 1tates "as consolidated into one company, the 0merican Telephone andTelegraph *ompany &no" #no"n as 0TCT *orp!', "hich "as a regulated monopoly!6.-. RECENT EVELO/MENTS6.-.1. T#$ E)$r&$nc$ o, Bro'dc'!tin&Telephones and telegraphs are primarily private means of communications, sending signals fromone point to another, but "ith the invention of the radio, public communications, or point-to-multipoint signals, could be sent through a central transmitter to be received by anyone

possessing a receiver! $talian inventor and electrical engineer 9uillermo +arconi transmitted a

+orse-code telegraph signal by radio in @D! This began a revolution in "ireless telegraphy that"ould later result in broadcast radios that could transmit actual voice and music!

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! Telecommunications, devices and systems that transmit electronic or optical signals acrosslong distances!7! Telecommunications usually involves a sender of information and a single recipients lin#ed bya technology, such as a telephone system, that transmits information from one place to another!3! Telecommunications devices convert different types of information, such as sound and video,

into electronic or optical signals!5! The messages can be sent from one sender to a single receiver&point-to-multipoint'or from onesender to many receivers &point-to-point'!D! *onsolidation occurred in the telegraph industry &as it has in numerous telecommunicationsindustries', and by the @2 s the %estern 4nion Telegraph *ompany emerged as the dominantoperator!! Early telephones required direct connections to other telephones, but this problem "as solved"ith telephone e)change s"itches, the first of "hich "as installed in >e" ?aven, *onnecticut,in 2 !2! Telephones and telegraphs are primarily private means of communications, sending signalsfrom one point to another, but "ith the invention of the radio, public communications, or point-

to-point signals, could be sent through a central transmitter to be received by anyone possessinga receiver!!

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T'0%$ 6.1T"($ o, d$ ic$ T"($ o,

)$!!'&$M$diu) o,

tr'n!)i!!ionA((%ic'tion

Nu)0$r o,r$ci(i$nt!

C. LAN*UA*E 9OCUS: A VERBS USE 9OR /RESENTIN* T E SE;UENCE O9EVENTST#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( %'n&u'&$ '+'r$n$!! in t$r)! o, u!$ o,'d $r0! +#$n (r$!$ntin& t#$ !$3u$nc$ o, $ $nt! or 'ction!. C.1. S$%$ct t#$ !uit'0%$ 'd $r0! ,ro) t#$ %i!t 0$%o+ 'nd u!$ t#$) to %in t+o!$nt$nc$!5 in 'ccord'nc$ +it# t#$ in,or)'tion (ro id$d 0" !$ction 6.2 o, t#$ t$ t.Li!t 6.1.T EN5 EREA9TER5 T EREA9TER5 A9TER AR S5 BE9ORE5 SOON A9TER

4T AT75 SUBSE;UENTLY5 /RIOR5 AT T E SAME TIME5 MEAN ILE5 LATER59IRST4LY75 SECON 4LY75 SIMULTANEOUSLY.< !o)$ ('ir! o, !$nt$nc$! c'n 0$ %in $d 0" !$ $r'% o, t#$ 'd $r0! in t#$ %i!t.! 0merican art professor 1amuel .! /! +orse pursued an interest in electromagnetism to createa practical electromagnetic telegraph in 32! $n 53 +orse built a demonstration telegraph lin#

bet"een %ashington, 6!*!, and /altimore, +aryland!7! Telegraph use quic#ly spread; the first transcontinental lin# "as completed in ! /eginningin the mid- s, the telegraph delivered the first intercity, transcontinental, and transoceanicmessages in the "orld!3! $n 2 0merican inventor 0le)ander 9raham /ell ushered in a ne" era of voice and soundtelecommunication "hen he uttered to his assistant the terms, 8+r! %atson, come here; $ "ant

you,8 using a prototype telephone! /ell received the patent for the first telephone, but he had tofight numerous legal challenges to his patent from other inventors "ith similar devices!5!

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3! Ba destinaGie, dispozitivul de receptare, transformI semnalul din nou Hn mesa=!E. S/EAKIN*T#$ (ur(o!$ o, t#$!$ $ $rci!$! i! to d$ $%o( !($' in& ! i%%! +it# ' ,ocu! on (r$!$ntin& t#$c#rono%o&ic'% ord$r o, $ $nt!. E.1. T' in& turn!5 d$!cri0$ t#$ $ o%ution o, t$%$(#on$ !"!t$)! $'c# o, "ou

(r$!$ntin& t#$ on$ i)(ort'nt !t'&$. E)(#'!i=$ t#$ c#rono%o&ic'% ord$r o, t#$ !t'&$!.

Unit >

TELECOMMUNICATIONS O/ERATION/RINCI/LES

AIM: To recognize the English technical terms related to the operation oftelecommunication systems and devices;


- identify correctly the terms describing signal creating-,receiving-, transmitting processes;

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- recognise the specific terms related to signal encoding anddecoding procedures and the corresponding devices;

- describe the separate stages in the operation of telegraph-,telephone-, radio-, television-, and internet communications and identifysimilarities and differences;

- identify the types of equipment used for each type of signalcreation, transmission and reception and compare them;

- describe the function performed by each device;

- assimilate at least 3 terms specific of signal creating-,receiving-, transmitting processes and equipment;

KEY TERMS:

convert, digital format, mathematical format, transmission, decode, modulated electricalimpulses, via, modulation, contact, telegraph key, metal conductor, electrical impulse, burst of

sound, dots and dashes, diaphragm, wire coil, analogue waveform, electrical waveform, speaker, cellular radio telephones, broadcast radio, electromagnetic radiation, microwave,wavelength, frequency, encode, amplitude, tuner, picture tube, electron gun, photo-sensitivedisplay screen, analogue transmission, series of binary numbers, digits, network, broadbandnetworks, cable television company, modem, modulator/demodulator, transmission media,copper wires, fibre-optic cable, communication satellite, microwave radio, wire-based (or wireline) telecommunications, wireless communications, cordless telephone, pager, satellite, high-

speed nternet access!

o+ T$%$co))unic'tion! or !>.1. iNTRO UCTION

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Telecommunications begin "ith messages that are converted into electronic or optical signals!1ome signals, such as those that carry voice or music, are created in an analogue or "ave format,

but may be converted into a digital or mathematical format for faster and more efficienttransmission! The signals are then sent over a medium to a receiver, "here they are decoded bac#into a form that the person receiving the message can understand! There are a variety of "ays to

create and decode signals, and many different "ays to transmit signals!>.2. CREATIN* AN RECEIVIN* T E SI*NAL>.2.1. T$%$&r'(#6evices such as the telegraph and telephone relay messages by creating modulated electricalimpulses, or impulses that change in a systematic "ay! These impulses are then sent along "ires,through the air as radio "aves, or via other media to a receiver that decodes the modulation! Thetelegraph, the earliest method of delivering telecommunications, "or#s by converting thecontacts &connections bet"een t"o conductors that permit a flo" of current' bet"een a telegraph#ey and a metal conductor into electrical impulses! These impulses are sent along a "ire to areceiver, "hich converts the impulses into short and long bursts of sound or into dots and dasheson a simple printing device! 1pecific sequences of dots and dashes represent letters of the

alphabet! $n the early days of the telegraph, these sequences "ere decoded by telegraphoperators! $n this "ay, telegraph operators could transmit and receive letters that spelled terms!Bater versions of the telegraph could decipher letters and numbers automatically! Telegraphshave been largely replaced by other forms of telecommunications, such as electronic mail &e-mail', but they are still used in some parts of the "orld to send messages!>.2.2. T$%$(#on$The telephone uses a diaphragm &small membrane' connected to a magnet and a "ire coil toconvert sound into an analogue or electrical "aveform representation of the sound! %hen a

person spea#s into the telephoneJs microphone, sound "aves created by the voice vibrate thediaphragm, "hich in turn creates electrical impulses that are sent along a telephone "ire! ThereceiverJs "ire is connected to a spea#er, "hich converts the modulated electrical impulses bac#

into sound!>.2.-. R'dio/roadcast radio and cellular radio telephones are e)amples of devices that create signals bymodulating radio "aves! 0 radio "ave is one type of electromagnetic radiation, a form of energythat travels in "aves! +icro"aves are also electromagnetic "aves, but "ith shorter "avelengthsand higher frequencies! $n telecommunications, a transmitter creates and emits radio "aves! Thetransmitter electronically modulates or encodes sound or other information onto the radio "aves

by varying either the amplitude &height' of the radio "aves, or by varying the frequency&number' of the "aves "ithin an established range! 0 receiver &tuner' tuned to a specificfrequency or range of frequencies "ill pic# up the modulation added to the radio "aves! 0spea#er connected to the tuner converts the modulation bac# into sound!>.2.?. T$%$ i!ion/roadcast television "or#s in a similar fashion! 0 television camera ta#es the light reflectedfrom a scene and converts it into an electronic signal, "hich is transmitted over high-frequencyradio "aves! 0 television set contains a tuner that receives the signal and uses that signal tomodulate the images seen on the picture tube! The picture tube contains an electron gun thatshoots electrons onto a photo-sensitive display screen! The electrons illuminate the screen"herever they fall, thus creating moving pictures!

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Telegraphs, telephones, radio, and television all "or# by modifying electronic signals, ma#ingthe signals imitate, or reproduce, the original message! This form of transmission is #no"n asanalogue transmission! *omputers and other types of electronic equipment, ho"ever, transmitdigital information! 6igital technologies convert a message into an electronic or optical form first

by measuring different qualities of the message, such as the pitch and volume of a voice, many

times! These measurements are then encoded into multiple series of binary numbers, or s ands! .inally, digital technologies create and send impulses that correspond to the series of s ands! 6igital information can be transmitted faster and more clearly than analogue signals, becausethe impulses only need to correspond to t"o digits and not to the full range of qualities thatcompose the original message, such as the pitch and volume of a human voice! %hile digitaltransmissions can be sent over "ires, cables or radio "aves, they must be decoded by a digitalreceiver! >e" digital telephones and televisions are being developed to ma#etelecommunications more efficient!>.2.@. Co)(ut$r!(ersonal computers primarily communicate "ith each other and "ith larger net"or#s, such as the$nternet, by using the ordinary telephone net"or#! $ncreasing numbers of computers rely on

broadband net"or#s provided by telephone and cable television companies to send te)t, music,and video over the $nternet at high speeds! 1ince the telephone net"or# functions by convertingsound into electronic signals, the computer must first convert its digital data into sound!*omputers do this "ith a device called a modem, "hich is short for modulatorKdemodulator! 0modem converts the stream of s and s from a computer into an analogue signal that can then

be transmitted over the telephone net"or#, as a spea#erJs voice "ould! The modem of thereceiving computer demodulates the analogue sound signal bac# into a digital form that thecomputer can understand!>.-. TRANSMITTIN* T E SI*NALTelecommunications systems deliver messages using a number of different transmission media,including copper "ires, fibre-optic cables, communication satellites, and micro"ave radio! One

"ay to categorize telecommunications media is to consider "hether or not the media uses "ires!%ire-based &or "ire line' telecommunications provide the initial lin# bet"een most telephonesand the telephone net"or# and are a reliable means for transmitting messages!Telecommunications "ithout "ires, commonly referred to as "ireless communications, usetechnologies such as cordless telephones, cellular radio telephones, pagers, and satellites!%ireless communications offer increased mobility and fle)ibility! $n the future some e)perts

believe that "ireless devices "ill also offer high-speed $nternet access!

You )'" +'nt to &o 0'c to t#$ $" +ord! %i!t$d 't t#$ 0$&innin& o, t#$ unit 'nd c#$ct#'t "ou 'r$ ,')i%i'r +it# $'c# on$. *i $ t#$ir Ro)'ni'n $3ui '%$nt! 4i, n$c$!!'r"5 "ou c'nu!$ t#$ &%o!!'r" (ro id$d 't t#$ $nd o, t#$ t$ t0oo 7.

E8ERCISES

E8ERCISES

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A. REA IN*T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( r$'din& !tr't$&i$! 'nd r$in,orc$ to(icr$%'t$d oc'0u%'r"5 not to c#$c 0'c &round no+%$d&$.A.1. ' in& r$'d t#$ t$ t5 'n!+$r t#$ ,o%%o+in& 3u$!tion! 4t#$ !($ci,ic'tion! in 0r'c $t!r$,$r to t#$ !$ction in t#$ t$ t +#$r$ t#$ 'n!+$r c'n 0$ ,ound7:

! %hat is the means of creating a signal in telegraph communicationsL7! %hat is the means of creating a signal in telephone communicationsL3! %hat is the means of creating a signal in radio communicationsL5! %hat is the means of creating a signal in televisionLD! %hat is the means of creating a signal in computer-basedLA.2. 9i%% in t#$ ,o%%o+in& t'0%$ +it# in,or)'tion '0out !i&n'% )'ni(u%'tion &i $n in t#$ t$ t.T'0%$ >.1

T"($ o,t$%$co).!"!t$)

$ ic$!u!$d in!i&n'%

cr$'tion

$ ic$!u!$d ,or

!i&n'%r$c$(tion

Tr'n!)i!!ion!($$d

Tr'n!)i!!ion)$di'

T"($ o,!"!t$)

4+ir$%$!!+ir$

0'!$d7

B. VOCABULARY ORK T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to (ro)ot$ t#$ 'c3ui!ition o, n$+ %$ ic'% it$)! 0"(ro idin& co%%oc'tion!5 t$r)! ,o%%o+$d 0" (r$(o!ition! %$ ic'% !$t! 'nd tr'n!%'tion! o, t#$t$r)! con!id$r$d r$%$ 'nt to t#$ to(ic.B.1. M'tc# t#$ o($r'tion (rinci(%$! d$!cri0$d 0$%o+ +it# t#$ t"($ o, t$%$co))unic'tion!"!t$) in t#$ %i!t.

! The earliest method of delivering telecommunications, "or#s by converting thecontacts

&connections bet"een t"o conductors that permit a flo" of current' bet"een a telegraph #ey anda metal conductor into electrical impulses! These impulses are sent along a "ire to a receiver,"hich converts the impulses into short and long bursts of sound or into dots and dashes on asimple printing device! 1pecific sequences of dots and dashes represent letters of the alphabet!7! The transmitter electronically modulates or encodes sound or other information onto the radio"aves by varying either the amplitude &height' of the radio "aves, or by varying the frequency&number' of the "aves "ithin an established range! 0 receiver &tuner' tuned to a specificfrequency or range of frequencies "ill pic# up the modulation added to the radio "aves! 0spea#er connected to the tuner converts the modulation bac# into sound!3! 0 modem converts the stream of s and s from a computer into an analogue signal that canthen be transmitted over the telephone net"or#, as a spea#erJs voice "ould! The modem of thereceiver demodulates the analogue sound signal bac# into a digital form!a! telephone

b! telegraphc! computer d! televisione! radio

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B.2. In $'c# !$ri$! o, ,our t$r)! &i $n 0$%o+ t#$r$ i! on$ t$r) t#'t do$! not 0$%on& in t#$!$ri$!. Und$r%in$ t#$ oddD +ord 'nd u!ti," "our d$ci!ion5 '! !#o+n in t#$ ,o%%o+in&$ ')(%$:$.&.: digital format, mathematical format, transmission, dots and dashes ! ! diaphragm, "ire coil, cable television companies, cordless telephones!

7! high-speed $nternet access, "avelength, frequency, encode!3! photo-sensitive display screen, analogue transmission, series of binary numbers, contacts!5! communication satellites,, contacts, telegraph #ey, metal conductor, electrical impulses!D! modem, encode, micro"ave radio, fibre-optic cable!C. LAN*UA*E 9OCUS: COM/ARISON AN CONTRASTT#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( %'n&u'&$ '+'r$n$!! in t$r)! o,$ (r$!!in& co)('ri!on 'nd t$'c# contr'!ti $ con unction!. C.1. R$'d t#$ !$nt$nc$! 0$%o+ 'nd id$nti," !i)i%'riti$! 'nd di,,$r$nc$! o, t#$ t#in&!d$!cri0$d.! +icro"aves are also electromagnetic "aves, but "ith shorter "avelengths and higher

frequencies!

7! This form of transmission is #no"n as analogue transmission! *omputers and other types ofelectronic equipment, ho"ever, transmit digital information!3! 6igital information can be transmitted faster and more clearly than analogue signals, becausethe impulses only need to correspond to t"o digits and not to the full range of qualities thatcompose the original message, such as the pitch and volume of a human voice!5! %hile digital transmissions can be sent over "ires, cables or radio "aves, they must bedecoded by a digital receiver!D! /roadcast television "or#s in a similar fashion as radio! C.2. Id$nti," t#$ t$r)! t#'t r$nd$r contr'!ti $ )$'nin&. C.-. Co)(%$t$ t#$ %i!t 0$%o+ +it# ot#$r t$r)! +it# !i)i%'r )$'nin&.o+$ $r5 n$ $rt#$%$!!5 0ut5 on t#$ ot#$r #'nd5 d$!(it$ o,5 in !(it$ o,5 r$&'rd%$!! o,5 "$t5'%t#ou $ $n t#ou $ $n i,5 $tc.. TRANSLATIONT#$ (ur(o!$ o, t#i! $ $rci!$ i! to d$ $%o( tr'n!%'tin& ! i%%!. .1. Tr'n!%'t$ t#$ ,o%%o+in& t$r)! into En&%i!#:! semnal optic7! demodulare3! modulare5! undI radioD! lungime de undI! impuls electric2! undI electromagneticI! microundI@! medii de transmisie! fibrI opticI

E. S/EAKIN*T#$ (ur(o!$ o, t#$!$ $ $rci!$! i! to d$ $%o( !($' in& ! i%%! +it# ' ,ocu! on E.1. C#oo!$ on$ o, t#$ t$%$co))unic'tion! !"!t$)! d$!cri0$d in t#$ t$ t. or in('ir!5 co)('rin& t#$ t+o c#o!$n t$%$co))unic'tion! !"!t$)! u!in& t#$ ,o%%o+in& ('tt$rn!.

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M is considerably cheap erK moreefficient T?0> Avery muchquite a lotrather some"hat

slightlyscarcelyhardlyonly =ust M is e)actly the same as A precisely =ustvirtually

practicallymore or less

almostnearlyappro)imately M is totally different from A completely entirely quite M and A are dissimilar in every respect different "ay

Unit F

COMMUNICATION NET ORKS

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AIM: To recognize the English technical terms related to communication net"or#s;


- identify correctly the terms defining all types of transmissionmedia;

- recognise the specific terms related to cable net"or#s, radio"aves and communications satellites;

- describe the components of communications net"or#s;

- identify the types of equipment used for obtaining reliablesignal transmission;

- describe the operation principle of each type ofcommunication net"or#;

- assimilate at least 3 terms specific of signal transmission;

KEY TERMS:

wire, cable, telecommunications services, to connect, telephone switching facility, coaxial cable,video channel, subscriber, head-end, amplifier, process, retransmit, fibre-optic cable, pulsedbeams of laser light, pulses of light, "backbone" link, nternet traffic, antenna, #M and $Mradio, beam, dish-shaped antenna, high-capacity link, ionosphere, orbit, geostationary or

geosynchronous orbit, %arth&s rotation, coverage area, relay function, "bent pipes"!

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COMMUNICATION NET ORKSF.1. IRES AN CABLES%ires and cables "ere the original medium for telecommunications and are still the primarymeans for telephone connections! %ire line transmission evolved from telegraph to telephoneservice and continues to provide the ma=ority of telecommunications services! %ires connecttelephones together "ithin a home or business and also connect these telephones to the nearesttelephone s"itching facility!Other "ire line services employ coa)ial cable, "hich is used by cable television to provide

hundreds of video channels to subscribers! +uch of the content transmitted by the coa)ial cableof cable television systems is sent by satellite to a central location #no"n as the head end!*oa)ial cables flo" from the head end throughout a community and on"ard to individualresidences and, finally, to individual television sets! /ecause signals "ea#en as distance from thehead end increases, the coa)ial cable net"or# includes amplifiers that process and retransmit thetelevision signals!F.2. 9IBRE O/TICS CABLE.ibre-optic cables use specially treated glass that can transmit signals in the form of pulsed

beams of laser light! .ibre-optic cables carry many times more information than copper "irescan, and they can transmit several television channels or thousands of telephone conversations atthe same time! .ibre-optic technology has replaced copper "ires for most transoceanic routes

and in areas "here large amounts of data are sent! This technology uses laser transmitters tosend pulses of light via hair-thin strands of specially prepared glass fibres! >e" improvements promise cables that can transmit millions of telephone calls over a single fibre! 0lready fibreoptic cables provide the high capacity, Nbac#bone8 lin#s necessary to carry the enormous andgro"ing volume of telecommunications and $nternet traffic!F.-. RA IO AVES%ireless telecommunications use radio "aves, sent through space from one antenna to another,as the medium for communication!

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*ommunications satellites provide a means of transmitting telecommunications all over theglobe, "ithout the need for a net"or# of "ires and cables! They orbit Earth at a speed thatenables them to stay above the same place on Earth at all times! This type of orbit is calledgeostationary or geosynchronous orbit because the satelliteJs orbital speed operates insynchronicity "ith EarthJs rotation! The satellites receive transmissions from Earth and transmit

them bac# to numerous Earth station receivers scattered "ithin the receiving coverage area of thesatellite! This relay function ma#es it possible for satellites to operate as 8bent pipes8 that is,"ireless transfer stations for point-to-point and point-to-multipoint transmissions!*ommunications satellites are used by telephone and television companies to transmit signalsacross great distances! 1hip, airplane, and land navigators also receive signals from satellites todetermine geographic positions!


E8ERCISES A. REA IN*T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( r$'din& !tr't$&i$! 'nd r$in,orc$ to(icr$%'t$d oc'0u%'r"5 not to c#$c 0'c &round no+%$d&$.A.1. Loo t#rou t#$ t$ t 'nd 'n!+$r t#$ ,o%%o+in& 3u$!tion!:! %hich is the original medium for telecommunications and the primary means for telephoneconnectionsL7! %hich type of cable is used by cable television to provide hundreds of video channels tosubscribersL3! %hy is it necessary for the coa)ial cable net"or# to include amplifiers that process andretransmit the television signalsL

5! %hat #ind of transmission medium is used for cordless telephones and "ireless radiotelephone services, such as cellular radio telephones and pagersLD! %hat is the name of communications satellites that provide a means of transmittingtelecommunications all over the globe, "ithout need for a net"or# of "ires and cables byorbiting Earth at a speed that enables them to stay above the same place on Earth at all times!A.2. R$ r$'d t#$ t$ t 'nd d$cid$ on t#$ u!$!5 'd 'nt'&$! 'nd di!'d 'nt'&$! o, t#$ t"($! o,co))unic'tion n$t+or ! %i!t$d 0$%o+:Li!t F.1

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! *oa)ial cable net"or#s7! .ibre-optic cable net"or#s3!

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E.2. Ro%$ (%'":*rou( A: You 'r$ !'%$! )'n'&$r o, ' %'r&$ co' i'% c'0%$ )'nu,'cturin& co)('n".*rou( B: You 'r$ !'%$! )'n'&$r o, ' %'r&$ ,i0r$ o(tic c'0%$ )'nu,'cturin& co)('n".*rou( C: You 'r$ !'%$! )'n'&$r o, ' %'r&$ 'nt$nn'$ )'nu,'cturin& co)('n".I)'&in$ "ou 'r$ in ' con,$r$nc$ r$&'rdin& t#$ con!o%id'tion o, t#$ t$%$co))unic'tion!

!"!t$) o, Ro)'ni' 'nd "ou )u!t con inc$ t#$ contr'ctin& ('rt" o, t#$ 'd 'nt'&$! o, t#$co)('n" "ou r$(r$!$nt.

Unit G

TELECOMMUNICATIONS SYSTEMS

AIM: To recognize the English technical terms related to telecommunications systems;


- identify correctly the terms defining all types oftelecommunications systems;

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- recognise the specific terms related to the telecommunicationsdevices used in each system;

- describe the main components of each system;

- identify the types of equipment used for different types oftransmission;

- describe the processes that underlie the operation of each typeof device;

- assimilate at least 3 terms specific of telegraph-, telephone-,teletype-, tele)-, and facsimile transmission;

KEY TERMS:

switching station, technology, high-speed broadband connections, multimedia information,

telegram, receiving party, wireless telegraphy, land-based station, voice communications, datacommunications, low-voltage direct current, network switches, microwave relay station, textdelivery system, teletype system, telex system, facsimile machine (fax machine), terminal, telexkeyboard, graphics, optical scanner, coded information, printer!

T$%$co))unic'tion! S"!t$)!G.1. INTRO UCTION$ndividual people, businesses, and governments use many different types of telecommunicationssystems! 1ome systems, such as the telephone system, use a net"or# of cables, "ires, ands"itching stations for point-to-point communication! Other systems, such as radio and television,

broadcast radio signals over the air that can be received by anyone "ho has a device to receive

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them! 1ome systems ma#e use of several types of media to complete a transmission! .ore)ample, a telephone call may travel by means of copper "ire, fibre-optic cable, and radio "avesas the call is sent from sender to receiver! 0ll telecommunications systems are constantlyevolving as telecommunications technology improves! +any recent improvements, for e)ample,offer high-speed broadband connections that are needed to send multimedia information over the

$nternet!G.2. TELE*RA/Telegraph services use both "ire line and "ireless media for transmissions! 1oon after theintroduction of the telegraph in 55, telegraph "ires spanned the country! Telegraph companiesmaintained a system of "ires and offices located in numerous cities! 0 message sent by telegraph"as called a telegram! Telegrams "ere printed on paper and delivered to the receiving party bythe telegraph company! %ith the invention of the radio in the early @ s, telegraph signalscould also be sent by radio "aves! %ireless telegraphy made it practical for ocean-going ships as"ell as aircraft to stay in constant contact "ith land-based stations!G.-. TELE/ ONEThe telephone net"or# also uses both "ire line and "ireless methods to deliver voice

communications bet"een people, and data communications bet"een computers and people orother computers! The part of the telephone net"or# that currently serves individual residencesand many businesses operates in an analogue mode, uses copper "ires, and relays electronicsignals that are continuous, such as the human voice! 6igital transmission via fibre-optic cablesis no" used in some sections of the telephone net"or# that send large amounts of calls over longdistances! ?o"ever, since the rest of the telephone system is still analogue, these digital signalsmust be converted bac# to analogue before they reach users! The telephone net"or# is stable andreliable, because it uses its o"n "ire system that is po"ered by lo"-voltage direct current fromthe telephone company! Telephone net"or#s modulate voice communications over these "ires!0 comple) system of net"or# s"itches maintains the telephone lin#s bet"een callers! Telephonenet"or#s also use micro"ave relay stations to send calls from place to place on the ground!

1atellites are used by telephone net"or#s to transmit telephone calls across countries and oceans!G.?. TELETY/E5 TELETE8T AN 9ACSIMILE TRANSMISSIONTeletype, tele), and facsimile transmission are all methods for transmitting te)t rather thansounds! These te)t delivery systems evolved from the telegraph! Teletype and tele) systems stille)ist, but they have been largely replaced by facsimile machines, "hich are ine)pensive and

better able to operate over the e)isting telephone net"or#! The $nternet increasingly provides aneven more ine)pensive and convenient option! The teletype, essentially a printing telegraph, is

primarily a point-to-multipoint system for sending te)t! The teletype converts the same pulsesused by telegraphs into letters and numbers, and then prints out readable te)t! $t "as often used

by ne"s media organizations to provide ne"spaper stories and stoc# mar#et data to subscribers!Tele) is primarily a point-to-point system that uses a #eyboard to transmit typed te)t overtelephone lines to similar terminals situated at individual company locations!.acsimile transmission no" provides a cheaper and easier "ay to transmit te)t and graphics overdistances! .a) machines contain an optical scanner that converts te)t and graphics into digital, ormachine-readable, codes! This coded information is sent over ordinary analogue telephone linesthrough the use of a modem included in the fa) machine! The receiving fa) machineJs modemdemodulates the signal and sends it to a printer also contained in the fa) machine!

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E8ERCISES A. REA IN*T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( r$'din& !tr't$&i$! 'nd r$in,orc$ to(icr$%'t$d oc'0u%'r"5 not to c#$c 0'c &round no+%$d&$.

A.1. ' in& r$'d t#$ t$ t5 d$cid$ +#$t#$r t#$ in,or)'tion &i $n in t#$ !t't$)$nt! 0$%o+ i!tru$ 4T7 or ,'%!$ 497. Corr$ct t#$ ,'%!$ !t't$)$nt! 4t#$ !($ci,ic'tion! in 0r'c $t! r$,$r o t#$!$ction in t#$ t$ t +#$r$ t#$ 'n!+$r c'n 0$ ,ound7:! $ndividual people, businesses, and governments use the same type of telecommunicationssystems!7! 1ome systems, such as the telephone system, use a net"or# of cables, "ires, and s"itchingstations for point-to-multipoint communication!3! 1ome systems ma#e use of several types of media to complete a transmission!5! Telegraph services use both "ire line and "ireless media for transmissions!D! %ire line telegraphy made it practical for ocean-going ships as "ell as aircraft to stay inconstant contact "ith land-based stations!

! The part of the telephone net"or# that currently serves individual residences and many businesses operates in an analogue mode, uses copper "ires, and relays electronic signals that arecontinuous, such as the human voice!2! The telephone net"or# is stable and reliable, because it uses its o"n "ire system that is

po"ered by high-voltage alternating current from the telephone company!! Teletype, tele), and facsimile transmission are all methods for transmitting sounds rather thante)t!@! .a) machines contain an optical scanner that converts te)t and graphics into digital, ormachine-readable, codes!! The receiving fa) machineJs modem demodulates the signal and sends it to a printer outside

the fa) machine!

A.2. 9i%% in t#$ ,o%%o+in& t'0%$ +it# in,or)'tion '0out t$%$co))unic'tion! !"!t$)! &i $n int#$ t$ t. So)$ o, t#$ !('c$! )'" r$)'in 0%'n 5 '! t#$ in,or)'tion i! not &i $n. T'0%$ G.1.T"($ o,t$%$co))unic'tion! !"!t$)

$ ic$!$)(%o"$d init! o($r'tion

O($r'tion(rinci(%$

T"($ o,in,or)'tiontr'n!)itt$d

U!$ Curr$nti)(ort'nc$

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B. VOCABULARY ORK T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to (ro)ot$ t#$ 'c3ui!ition o, n$+ %$ ic'% it$)! 0"(ro idin& co%%oc'tion!5 t$r)! ,o%%o+$d 0" (r$(o!ition! %$ ic'% !$t! 'nd tr'n!%'tion! o, t#$t$r)! con!id$r$d r$%$ 'nt to t#$ to(ic.B.1. M'tc# $'c# o, t#$ t$r)! in co%u)n A +it# ' +ord in co%u)n B:A Bfa) machineto demodulatetelephone net"or# #eyboardreliable

fiabila demodulatastaturIreGea de telefonieaparat fa)

B.2. 9i%% in t#$ &'(! in t#$ ,o%%o+in& !$nt$nc$! +it# t#$ t$r)! r'ndo)%" %i!t$d 0$%o+:Li!t G.1.aircraft , net"or#, fibre-optic cable, land-based, broadcast, "ireless, ships, copper "ire, toreceive, digital, sender, radio "aves, via, voice, "ire line, optic; T$ t G.1.

! Other systems, such as radio and television, radio signals over the air thatcan be received by anyone "ho has a device them!7! .or e)ample, a telephone call may travel by means of , , and

as the call is sent from to receiver!3! %ireless telegraphy made it practical for ocean-going as "ell as

to stay in constant contact "ith stations!

5! The telephone net"or# also uses both and methods to deliver communications bet"een people, and data communications bet"een computers and people or other computers!D! transmission via fibre- cables is no" used in some sections ofthe telephone that send large amounts of calls over long distances!

C. LAN*UA*E 9OCUS: ;UANTI9IERST#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( %'n&u'&$ '+'r$n$!! in t$r)! o,3u'nti,i$r! 'nd t#$ir u!$ +it# count'0%$ noun! 'nd uncount'0%$ noun!. C.1. Loo 't t#$ %i!t 0$%o+ 'nd d$cid$ +#ic# 3u'nti,i$r i! !uit'0%$ in t#$ &i $ncont$ t: Li!t G.2.MUCSOMELITTLEA /IECE O9A LOT O9LITTLE

MANY9EA SIN*LE/LENTY O9SEVERAL A NUMBER O99E

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! $ndividual people, businesses, and governments use different types oftelecommunications systems!7! systems ma#e use of several types of media to complete a transmission!3! recent improvement, for e)ample, offers high-speed broadband connections that areneeded to send multimedia information over the $nternet!

5! The telephone net"or# also uses both "ire line and "ireless methods to deliver voicecommunications bet"een people, and data communications bet"een computersand people or other computers!D! coded information is sent over ordinary analogue telephone linesthrough the use of a modem included in the fa) machine!

C.2. Ent$r t#$ ,o%%o+in& t$r)! und$r t#$ '((ro(ri't$ #$'din& in t#$ t'0%$ 0$%o+:Li!t G.-.information, data, #no"ledge, advance, progress, development, cooper, fibre-optics, medium,technology, feature, advantage, disadvantage, improvement, increase, decrease; T'0%$ G.-.

COUNTABLE UNCOUNTABLE

. TRANSLATIONT#$ (ur(o!$ o, t#i! $ $rci!$ i! to d$ $%o( tr'n!%'tin& ! i%%!..1. Tr'n!%'t$ t#$ ,o%%o+in& !$nt$nc$! into En&%i!#:! 4nele sisteme utilizeazI mai multe tipuri de medii de transmisie!7! 1pre e)emplu, un apel telefonic poate fi transmis prin intermediul cablurilor de cupru, alcablurilor de fibrI opticI, Pi al undelor radio succesiv!3! 0cea parte a reGelei de telefonie care deservePte locuinGe sau sedii de firmI funcGioneazI pe

principiul analogic utilizQnd cabluri de cupru!E. S/EAKIN*T#$ (ur(o!$ o, t#$!$ $ $rci!$! i! to d$ $%o( !($' in& ! i%%! +it# ' ,ocu! on d$!cri0in&!$ $r'% t$%$co))unic'tion! !"!t$)!5 t#$ir r$%i'0i%it" 'nd o($r'tion (rinci(%$!. E.1. /r$!$nt'tionM' $ ' 0ri$, (r$!$nt'tion o, t#$ t$%$(#on$ !"!t$).4M' $ !ur$ "ou inc%ud$ in,or)'tion '0out t#$ ($r,or)'nc$5 r$%i'0i%it"5 n$t+or 5tr'n!)i!!ion )$di'5 t"($ o, d't' tr'n!)i!!ion5 d$ ic$! 'nd co)(on$nt!5 o($r'tion(rinci(%$! 'nd (o!!i0%$ ,utur$ d$ $%o()$nt in t#$ ,i$%d7.

Unit 1H

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ATA TRANSMISSION AN COM/UTERNET ORKS

AIM: To recognize the English technical terms related to data transmission and computernet"or#s;


- identify correctly the terms defining radio-, television-, andcomputer technology;

- recognise the specific terms related to 9(1 and 9BO>011net"or#s;

- describe the functions performed by specialized equipment;

- identify the types of equipment used for data transmission andits operation principles;

- describe the different types of net"or#s;

- assimilate at least 3 terms specific of data transmission"ithin telecommunications net"or#s!

KEY TERMS:

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preset frequency, commercial broadcasts, within range, powerful transmitter, shortwave radio,electrically charged layer, commercial television, very high frequency (' $) radio waves,

ultrahigh frequency ( $) radio waves, teleconferencing, videophones, video camera, privateor public television, terrestrial links, scrambled signal, unscrambled signal, network operator, %uropean *hase #lternative +ine standard, high-resolution picture, sound quality, aspect ratio,

lobal *ositioning ystem ( * ), lobal .rbiting avigation atellite ystem ( +. # ), positioning information, * receiver, process of triangulation, military use, navigational tool,road maps, graphical information, * location data, audio services, video services, text

services, software services, multimedia services, ntegrated ervices 0igital etwork ( 0 ), 0igital ubscriber +ines (0 +), upgrade, high-speed data transmission, cable modem service,electronic mail (e-mail), text-based message delivery system, automated banking terminals,credit card transactions!

ATA TRANSMISSION AN COM/UTER NET ORKS1H.1. RA IO 5 TV COMMUNICATIONS1H.1.1. R'dio

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frequency & ?.' and ultrahigh frequency &4?.' radio "aves and can be received by anytelevision set "ithin range of the transmitter! Televisions have also been used for point-to-point,t"o-"ay telecommunications! Teleconferencing, in "hich a television picture lin#s t"o

physically separated parties, is a convenient "ay for businesspeople to meet and communicate"ithout the e)pense or inconvenience of travel! ideo cameras on computers no" allo" personal

computer users to teleconference over the $nternet! ideophones, "hich use tiny video camerasand rely on satellite technology, can also send private or public television images and have beenused in ne"s reporting in remote locations!*able television is a commercial service that lin#s televisions to a source of many different typesof video programming using coa)ial cable! The cable provider obtains coded, or scrambled,

programming from a communications satellite, as "ell as from terrestrial lin#s, including broadcast television stations! The signal may be scrambled to prevent unpaid access to the programming! The cable provider electronically unscrambles the signal and supplies the decodedsignals by cable to subscribers! Television users "ith personal satellite dishes can access satellite

programming directly "ithout a cable installation! (ersonal satellite dishes are also a subscriberservice! .ees are paid to the net"or# operator in return for access to the satellite channels!

+ost television sets outside of the 4nited 1tates that receive programming use different types ofstandards for receiving video signals! The European (hase 0lternative Bine standard generates ahigher-resolution picture than the sets used in the 4nited 1tates, but these television sets aremore e)pensive! +anufacturers no" offer digital video and audio signal processing, "hichfeatures even higher picture resolution and sound quality! The shape of the television screen ischanging as "ell, reflecting the aspect ratio &ratio of image height to "idth' used for movie

presentation!1H.2. I*ITAL COMMUNICATION NET ORKS1H.2.1. *%o0'% /o!itionin& 'nd N' i&'tion S"!t$)!The 4nited 1tates 9lobal (ositioning 1ystem &9(1' and the avigation1atellite 1ystem &9BO>011' are net"or#s of satellites that provide highly accurate positioning

information from any"here on Earth! /oth systems use a group of satellites that orbit around thenorth and south poles at an altitude of 2,D #m & ,@ mi'! These satellites constantly broadcast the time and their location above Earth! 0 9(1 receiver pic#s up broadcasts from thesesatellites and determines its position through the process of triangulation! 4sing the timeinformation from each satellite, the receiver calculates the time the signal ta#es to reach it!.actoring in this time "ith the speed at "hich radio signals travel, the receiver calculates itsdistance from the satellite! .inally, using the location of three satellites and its distance fromeach satellite, the receiver determines its position!9(1 services, originally designed for military use, are no" available to civilians! ?andheld 9(1receivers allo" users to pinpoint their location on Earth to "ithin a fe" meters! One type ofnavigational tool used in automobiles integrates a 9(1 receiver "ith an intelligent compact disc

player capable of displaying road maps and other graphical information! 4pon receiving the 9(1location data, the *6 player can pinpoint the location visually on one of the road maps containedon disc!1H.2.2. /$r!on'% Co)(ut$r!(ersonal computers use telecommunications to provide a transmission lin# for the delivery ofaudio, video, te)t, soft"are, and multimedia services! +any e)perts believe that the convergenceof these services "ill generate consumer demand for ne" generations of high-speed, broadbandnet"or#s! *urrently, the delivery of most of these audio, video, and te)t services occurs over

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e)isting telephone connections using the $nternet! 1ome computers connect directly to the digital portion of the telephone net"or# using the $ntegrated 1ervices 6igital >et"or# &$16>' or6igital 1ubscriber Bines &61B', but this requires special equipment at user locations! Telephoneand cable television companies must also ma#e upgrades to their lines so that they can handlehigh-speed data transmission! $n many locations companies and individuals "ith high-speed data

requirements no" have the option of securing 61B service from telephone companies and cablemodem service from cable television companies!Electronic mail, or e-mail, is a #ey attraction of the $nternet and a common form of computertelecommunications! E-mail is a te)t-based message delivery system that allo"s informationsuch as typed messages and multimedia to be sent to individual computer users! Bocal e-mailmessages &"ithin a building or a company' typically reach addressees by travelling through "ire-

based internal net"or#s! E-mail that must travel across to"n or across a country to reach thefinal destination usually travels through the telephone net"or#! Other computertelecommunications technologies that businesses frequently use include automated ban#ingterminals and devices for credit card transactions that bill charges directly to a customerJs ban#account!


E8ERCISES A. REA IN*T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( r$'din& !tr't$&i$! 'nd r$in,orc$ to(icr$%'t$d oc'0u%'r"5 not to c#$c 0'c &round no+%$d&$.

A.1. R$ r$'d !$ction 1H.1. 'nd 1H.2.2. 'nd d$cid$ on t#$ u!$! o, t#$!$ t"($! o,co))unic'tion!:1. R'dio2. T$%$ i!ion-. Co)(ut$r!A.2. In 1H.2.1. o, t#$ t$ t t#$ o($r'tion (rinci(%$! o, */S 'nd *LONASS 'r$ d$!cri0$d.E (%'in t#$ '((%ic'tion! t#'t t#$!$ !"!t$)! 'r$ )o!t !uit'0%$ ,or.B. VOCABULARY ORK T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to (ro)ot$ t#$ 'c3ui!ition o, n$+ %$ ic'% it$)! 0"(ro idin& co%%oc'tion!5 t$r)! ,o%%o+$d 0" (r$(o!ition! %$ ic'% !$t! 'nd tr'n!%'tion! o, t#$t$r)! con!id$r$d r$%$ 'nt to t#$ to(ic.

B.1. Ent$r in t#$ ,o%%o+in& t'0%$ in,or)'tion r$%'t$d to t$%$ i!ion 4!$$ 1H.1.27:T"($ o, t$c#no%o&" Tr'n!)i!!ion)$di'

A((%ic'tion! St'nd'rd!

B.2. Add t#r$$ )or$ t$r)! to t#$ ,o%%o+in& %i!t!:

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1. t"o-"ay radios, cordless telephones, cellular radio telephones;2. very high frequency & ?.', t"o-"ay telecommunications, videophones;-. satellite, receiver, calculate;B.-. 9i%% in t#$ )i!!in& t$r)!:! The &9(1' and the &9BO>011' are net"or#s of satellites

that provide highly accurate positioning information from any"here on Earth!7! /oth systems use a group of that around the north and south poles at a of 2,D #m & ,@ mi'!3! ?andheld 9(1 allo" users to their location on Earth to "ithin a fe"meters!5! 1ome computers connect directly to the digital portion of the telephone net"or# using the

&$16>' or &61B', but this requires special equipment atuser locations!D! *ommercial television is broadcast over & ?.' and &4?.'radio "aves and can be received by any television set "ithin range of the transmitter!C. LAN*UA*E 9OCUS: ACRONYMS AN ABBREVIATIONS

T#$ (ur(o!$ o, t#$ ,o%%o+in& $ $rci!$! i! to d$ $%o( %'n&u'&$ '+'r$n$!! in t$r)! o,'cron")! 'nd '00r$ i'tion!. C.1. In t#$ t$c#nic'% r$&i!t$r "ou +i%% ,r$3u$nt%" $ncount$r )u%ti +ord t$r)! t#'t'r$ not (ronounc$d in t#$ir co)(%$t$ ,or)5 t#$ir 'cron")! or '00r$ i'tion! 'r$ u!$din!t$'d. 9ind 't %$'!t ,i $ !uc# t$r)! 'nd t#$ir 'cron")! in t#$ t$ t. C.2. R$'d t#$ ,o%%o+in& 'cron")! 'nd '00r$ i'tion! 'nd d$cid$ on t#$ corr$ct +'"to (ronounc$ t#$) 4'! ' n$+ +ord r$'din& t#$ %$tt$r! !$('r't$%"7 'nd id$nti," t#$ co)(%$t$t$r). Li!t 1H.1.

1. 4?.2. ?.-.

9(1?. 9BO>011@. *66. $16>>. (*F. 61BG. E-mail1H. mi

C.-. #'t 'r$ t#$ corr$!(ondin& Ro)'ni'n 'cron")! 'nd '00r$ i'tion!. C.?. T#in o, ot#$r 1H '00r$ i'tion! or 'cron")! t#'t "ou 'r$ ,')i%i'r +it#. . TRANSLATIONT#$ (ur(o!$ o, t#i! $ $rci!$ i! to d$ $%o( tr'n!%'tin& ! i%%!. .1. Tr'n!%'t$ t#$ ,o%%o+in& t$ t into Ro)'ni'n.(ersonal radio communication is generally limited to short distances &usually a fe" #ilometers',

but po"erful transmitters can send broadcast radio signals hundreds of #ilometers! 1hort"averadio, popular "ith amateur radio enthusiasts, uses a range of radio frequencies that are able to

bounce off the ionosphere! This electrically charged layer of the atmosphere reflects certainfrequencies of radio "aves, such as short"ave frequencies, "hile allo"ing higher-frequency

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"aves, such as micro"aves, to pass through it! 0mateur radio operators use the ionosphere to bounce their radio signals to other radio operators thousands of #ilometers a"ay!E. S/EAKIN*T#$ (ur(o!$ o, t#$!$ $ $rci!$! i! to d$ $%o( !($' in& ! i%%! +it# ' ,ocu! on (r$!$ntin&di,,$r$nt '((%ic'tion! o, d't' tr'n!)i!!ion 'nd co)(ut$r n$t+or !.

E.1. #ic# 'r$5 in "our o(inion5 t#$ )o!t i)(ort'nt '((%ic'tion! o, */S 'nd *LONASS .Ju!ti," "our 'n!+$r.

unit 678910

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