S    a:ut_title.comS  5  O  ͻ  J 	DISK 2  O   ͼ   O       #	Understanding Telecommunications* Which Lesson would you like to work on?  A  Lesson 3: How Telephones Work	   B  Lesson 4: Making a Connection   C A different lesson G D@ Select A-C S  5 95  5  O  ͻ  J 	DISK 3  O   ͼ   O       #	Understanding Telecommunications= This course has 7 lessons, which are divided into 4 disks./ Please type the number of the disk you want:	 	 1 "	Disk 1 - Lesson 1: Introduction
 0
Lesson 2: Evolution of the Telephone Industry  2 )Disk 2 - Lesson 3: How Telephones Work
  
Lesson 4: Making a Connection  3 0Disk 3 - Lesson 5: Business Telephone Systems (Lesson 6: The Private Branch Exchange  4 .Disk 4 - Lesson 7: Telecommunication Trends  9@ Select 1-4 S  5  5  5  5  H 	DISK 2   #	Understanding TelecommunicationsC If you want to work on a lesson on another disk you will need to (Press the space bar to exit this disk
 5
Insert the correct disk, type GO, and press return( @!%C@ Press Space S 85	  @ @ @ @ 
@ @ @ @ @ @ @ @ @ @ @  @ "@ $@ &@ (@ *@ ,@ $-O                                 @ @ @ @ 
@ @ @ @ @ @ @ @ @ @ @  @ "@ $@ &@ (@ *@ ,@ $-O LESSON 3 - HOW TELEPHONES WORK  	@ 	@ 	@ 	@ 	
@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	 @ 	"@ 	$@ 	&@ 	(@ 	*@ 	,@ $	-O                                 
@
@
@
@

@
@
@
@
@
@
@
@
@
@
@
 @
"@
$@
&@
(@
*@%
,@S  0 
5   J 	LESSON 3   	IntroductionS  
  	      This lesson will introduce: @How the telephone converts a voice into an electrical messageS  7	    @How the telephone converts a voice into an electrical message
 4
How telephone circuits can transmit computer dataS 	  @How the telephone converts a voice into an electrical message
 4
How telephone circuits can transmit computer data 8How wire, cable, and other media transmit informationS 
  @How the telephone converts a voice into an electrical message
 4
How telephone circuits can transmit computer data 8How wire, cable, and other media transmit informationS  x  	

!ٱ
%
)ٱ
+Ŀ!$p         -x!$'*,p -

ͻ
!
$
'
*
,p 
-Ȼ!$'*,p -Ȼ ͱ
#p - .S More specifically, you will learn about how the telephone worked in 1876 when itP was developed by Alexander Graham Bell, and how modern telephones work today.S  7	   ********	**'	************************************Ŀ4  ? You will also learn about analog and digital transmission...S 
   aa#** a aa!*&* a a *'* a a*(*	****************	 aaaaaaaaaaaa	*********************** aaaa"Ŀ a a"%# aa%S    aa# aa1** a aa! a& a/*4* a a  a' a.*5* a a a( a-*6*!	******************************	, aaaaaaaaaaaa	8******** aaaa" aaaa0Ŀ a a" a% a03%1 aa3S    aa# aa1 aa?* a aa! a& a/ a4 a=* a a  a' a. a5 a<* a a a( a- a6 a;*/	********************************************
	: aaaaaaa aaaa" aaaa0 aaaa> a a" a% a0 a3 a>3? aS    aa# aa1 aa? a a aa! a& a/ a4 a= a a a  a' a. a5 a< a a a a( a- a6 a; a5	**************************************************	@ a aaaa" aaaa0 aaaa> aa a a" a% a0 a3 a> a4S  7	   p x @x            p x @x Kx 	p 			x 	@x 	Kx 
p 


t*
@x 
Kx x@x ---------- x  ?x
p 

p

p 
?x 
Ex        x?x1 ... and how they relate to data communication.S   
digital
Ŀ	 0 1 1 0
	MODEM

S   	%analog+..)...
0Ŀ	!.	(.	/.
	0MODEM
".
'.

0$..S   
7digital
	70 1 1 0	?S  2	   %&tĿ&t'             4t&t'             4t		&t 	(pMULTIPLEXER	3 	4t

&t 
(            
4t
5&t (            4t&t
%M You will then see how several calls can be sent over the same wire through multiplexing.S 0 	 % 	   @  %    P5 	 ? 	      %     2	  
''
%,,,, ' ,,,,',,,   ,, ' ,,(),+'-,,,.....5	8>?		'''	(	6	=_	>

(
3___
6(	"______(
	____________P A number of distribution systems will also be discussed to help you learn the important features ofwire and cable.S  7	  9____0[][]____(=)____[][]0[][]	8(____)B[][]	__	____/
[
HI!
][[__	__][_//\/\
/\
/\
/\/\/\/\//!\//\	\
/\/\/\///"\//\/
/\\/\/#\ ... as well asmicrowaveandsatellite'distribution systems.S   
[
 aaaaaaaa
HI!S   
 aaaaaaaa
HI!S   $!	 I
 aaaaaaaa
HS   .!)I$H	  A
 AS   . a) aF a$ aIH	MIS   
G aaaaaaa
G aaaaaaa		H aaaaaaS  2	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^O After learning this material, you will be asked to "put it all together" andO design a telephone system for the newly discovered island of Batwini and its capital city of Danimia.S  0 
5	  6 Please choose the topic you would like to see next.  A Introduction&' E 	-Unit 4	 	&	-Wire and Cable  B 	Unit 1&' F 	-Unit 5 Voice Communications&-Microwave and Satellite  C 	Unit 2&' G 	-Unit 6 Data Communications&-Putting It All Together  D 	Unit 3&' H -Exit this Lesson Multiplexing&S  5   5 A 5 b 5 r 5  5  5  5x  	

!ٱ
%
)ٱ
+Ŀ!$p         -x!$'*,p -

ͻ
!
$
'
*
,p 
-Ȼ!$'*,p -Ȼ ͱ
#p - .N This unit describes Bell's invention of the telephone in 1876, explains theJ principles underlying early telephone communications, and describes how telephones work today.S ! 2	   '(H $ooͿ8H H &oo78H H &oo	,LESSON4378H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2178H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 3, Unit 1.  After you have finished reading2 this material, press the space bar to continue.S " #" 5	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S # !# 5 ' #' 7  0 
5 GAlexander Graham Bell was issued a patent for the telephone in 1876. The patent mentioned the!variable resistance principle,<which involvedK
sending sound waves by changing the resistance in an electrical circuit.
 
The 
variable resistance principle&
&is still used to transmit telephonemessages today.' Do you want to review more material?S $ 2 " #" 5 5Speech produces variations in air pressure, called7acoustical energy,Jwhich!can be heard by the human ear.
 I
A telephone converts this acoustical energy into electrical energy, orNvariations in electrical current, which can be sent through wire or another
medium.' Do you want to review more material?S % 2 " #" 5 *A complete telephone circuit includes a,transmitter8which can convert a&sound into an electrical current, a(transmission medium<such as wire orD	cable to deliver the electrical current to its destination, and a	FreceiverFto turn the electrical current impulses back into an audible sound.' Do you want to review more material?S & 2 " #" 5 $When you speak into the telephone&transmitter1, it converts speech soundsJinto variations in electrical resistance which can be sent through some;	transmission media to the receiver of another telephone. 0You hear conversation through the telephone's2receiver:.  It converts theHvariations in electrical current back into variations in air pressure*which can be detected by the human ear.# This ends the review for Unit 1.S " #" 5	   - Today's telephones transmit voices by the:  A Variable voltage principle	   B  Variable resistance principle   C Magneto-induction principle S ( !(  ) !)  * !* S No.  Bell's original patent mentioned only two principles: the magneto-induction+ principle, which failed to work, and the )variable resistance principle
F, which is the correct answer.  Do you want another question?S + #+ 7 " #" 7 That's right.  The variable resistance principle 1shows that sound waves change, the electrical resistance of the circuit.  Do you want another question?S + #+ 7 " #" 7P No.  Bell was working on the magneto-induction principle when he patented the9 telephone, but it never worked.  He succeeded with the7variable resistance principle	,which is still used today.  Do you want another question?S + #+ 7 " #" 7J The first time Alexander Graham Bell successfully sent his voice over a0 telephone wire, the transmitter was based on:	 	 A %	A membrane placed next to a magnet
   B  An electromagnet speaker coil
   C $A wire immersed in water and acid S , !,  - !-  . !. L No.  Although Bell experimented with this type of transmitter, he did not succeed until he used a"wire immersed in water and acid8which produced variable resistance.  Do you want another question?S / "/ 7 " #" 7K No.  Bell did not use speaker transmitters at all.  His first successful transmitter was based on a"wire immersed in water and acid:.  Do you want another question?S / "/ 7 " #" 7P That's right.  As a diaphragm vibrated the wire, it changed the resistance in the electrical circuit.  Do you want another question?S / "/ 7 " #" 7 True or False?S Today's telephones convert acoustical energy using the same basic principle Bell
 and Watson's phone did.S 0 !0  1 !1  That's right, it'strue8that today's phones and Bell's both used the variable
 resistance
principle.  Do you want another question?S 2 #2 7 " #" 7O That's incorrect. Both today's phones and Bell's use the variable resistance
 principle.  Do you want another question?S 2 #2 7 " #" 7; A telephone transmitter converts acoustical energy into:  A 	Speech	   B Alternating current   C Electrical energy S 3 !3  4 !4  5 !5 O No.  Speech normally consists of acoustical energy.  A telephone transmitter converts this intoelectrical energy.  Do you want another question?S 6 #6 7 " #" 7R No.  Many household appliances use alternating current but the modern telephone9 does not.  The correct answer is the more general term7electrical energy.  Do you want another question?S 6 #6 7 " #" 7% That's right.  These variations in#electrical energy5can then be transmitted to a telephone receiver.  Do you want another question?S 6 #6 7 " #" 7O The diaphragm in a telephone transmitter vibrates in response to changes in:  A Air pressure	   B Carbon granules   C Electrical energy S 7 !7  8 !8  9 !9  That's right.Air pressure5begins the process of converting acoustical energy into electrical energy.  Do you want another question?S : ": 7 " #" 7M Not quite.  When the diaphragm in a transmitter moves, it does vibrate theM carbon granules.  But the diaphragm first begins to vibrate in response to
 changes inair pressure.  Do you want another question?S : ": 7 " #" 7O Incorrect.  A transmitter does not respond to electrical energy; it producesG electrical energy.  The diaphragm vibrates in response to changes inEair pressure.  Do you want another question?S : ": 7 " #" 7 True or False?S The principles used for telephone switching mechanisms today have changed little
 in the last century.S ; !;  < !<  No, the correct answer wasfalse' .  While the principles of telephoneL transmission have changed little in the last century, telephone switching& mechanisms are now quite different.  Do you want another question?S = #= 7 " #" 7 That's right, it's	false.6While the principles of telephone transmission have changed little inAthe last century, telephone switching mechanisms are now quite
 different.  Do you want another question?S = #= 7 " #" 7N Which of the following is a key component of a standard telephone receiver?  A Carbon granules	   B Acidulated water   C A magnet S >  >  ?  ?  @  @ M Incorrect.  Carbon granules are a part of the telephone transmitter; but a	 magnet.is a key component of a telephone receiver.& This ends the questions for Unit 1.S " #" 7	   R Incorrect.  Bell used acidulated water in his early designs, but it is not used in modern telephones.  Apermanent magnet'*is a key requirement for a receiver.& This ends the questions for Unit 1.S " #" 7	    That's right.  Apermanent magnet0"is a key requirement of a telephone receiver.S It provides a constant bias field for the electromagnetic field to work against.& This ends the questions for Unit 1.S " #" 7	   p x @x            p x @x Kx 	p 			x 	@x 	Kx 
p 


t*
@x 
Kx x@x ---------- x  ?x
p 

p

p 
?x 
Ex        x?xG This part of Lesson 3 describes two different types of transmission,	 analogand
digital9, and how they are related to computer communications.S B  
digital
Ŀ	 0 1 1 0
	MODEM

S C  	%analog+..)...
0Ŀ	!.	(.	/.
	0MODEM
".
'.

0$..S D  
7digital
	70 1 1 0	?S E 2	   '(H $ooͿ8H H &oo78H H &oo	,LESSON4378H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2278H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 3, Unit 2.  After you have finished reading2 this material, press the space bar to continue.S F #F 5	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S G !G 5 K "K 7  0 
5 FIn today's automated office, employees often need to have access toJinformation which may be located on several different computer systems.	A	Local Area Network6	(LAN) links information processing equipment withinIa building or other limited area by means of wire or coaxial cable and'
allows high-speed data transmission. HA wide-area network links computers and peripherals which are located(further away.  Every network requires*communications softwareBto translate0programs between computers and other devices.' Do you want to review more material?S H 2 F #F 5 Analog signals;are transmitted as continuous waves which are constantly2changing in frequency, just as sound waves are.
 $
Computers, on the other hand, use
&digital signals
6to represent information.NDigital signals consist of a discontinuous stream of on/off impulses (oftenLcoded as 0s and 1s) that can be stored and sorted more easily than analogsignals.' Do you want to review more material?S I 2 F #F 5 OAny signals can be represented in either analog or digital form.  Voices are>ordinarily analog, and computer data is ordinarily digital.
 O
The U.S. National Network was designed for voice communication, and consistsIprimarily of analog channels.  However, digital lines are increasingly.being used to transmit both voice and data.' Do you want to review more material?S J 7 F #F 5 AmodemDis a piece of hardware which converts digital computer data to anNanalog form for transmission over phone lines, and then converts the analogC	information back into a digital form for the receiving computer. (Transmission speed is measured in the*baud rate4or the number of bits perNsecond (bps) travelling across the line.  Modems are available for a numberEof different transmission speeds, typically from 300 to 9600 baud.# This ends the review for Unit 2.S F #F 5	    True or False?R When you speak into a telephone, your voice creates mechanical vibrations which-
 are usually converted into analog signals.S L !L  M !M 
 Yes, it istrue;that your voice is converted into an analog signal which resembles a wave.  Do you want another question?S N #N 7 F #F 7% That's incorrect, the statement is#true&'.  When you speak into a telephone,J your voice is converted into analog signals which have continuously and, smoothly varying amplitude and frequency.  Do you want another question?S N #N 7 F #F 7A A discontinuous stream of on/off impulses is a description of:  A A sine wave	   B An analog wave   C A digital signal S O !O  P !P  Q !Q K That's not it.  A sine wave, like an analog signal, has continuously and/ smoothly varying amplitude and frequency.  A-digital signal;, however, is discontinuous.  Do you want another question?S R "R 7 F #F 7M That's not right.  An analog signal has continuously varying amplitude and8 frequency and resembles a wave.  On the other hand, a6digital signalEconsists of a discontinuous bit stream.  Do you want another question?S R "R 7 F #F 7S You're right.  Unlike the smoothly varying amplitude and frequency of the analog signal, thedigital signal!is a discontinuous bit stream.  Do you want another question?S R "R 7 F #F 7 True or False?L The United States National Telephone Network consists primarily of analog
 channels.S S !S  T !T  Right, it'strue.=To transmit computer data over this network you must first6 convert the digital bit stream to an analog signal.  Do you want another question?S U #U 7 F #F 7  Sorry, the correct answer wastrue.*%At this time the U.S. telephone network doesconsist primarily of	analog!channels.  Do you want another question?S U #U 7 F #F 7+ Which transmission speed is the fastest?  A 300 baud	   B 1200 baud   C 9600 baud S V !V  W !W  X !X R Sorry.  300 baud, or 300 bits per second, is the slowest of these three speeds. The fastest is
9600 baud.  Do you want another question?S Y "Y 7 F #F 7S Sorry.  1200 baud, falls between 300 and 9600 baud.  Of these, the fastest speed is
9600 baud.  Do you want another question?S Y "Y 7 F #F 7S Very good.  Baud rate is equal to bits per second, and the more bits per second, the faster the transmission.  Do you want another question?S Y "Y 7 F #F 7 True or False?= Both voice and data can be transmitted as digital signals.S Z !Z  [ ![  That's right, it'strue:.  Although analog transmission is typically associated with voice, both analogand digital'$signals can transmit voice and data.  Do you want another question?S \ "\ 7 F #F 7 No, the correct answer wastrue-.  Although typically associated with data9 transmission, digital signals can also transmit voice.  Do you want another question?S \ "\ 7 F #F 7 True or False?Q A system in which several nearby computers can share data and communicate with-
 each other is called a local area network.S ] !]  ^ !^  That's right, it'strue<.  In a local area network, or LAN, several computers can share data and communicate.  Do you want another question?S _ "_ 7 F #F 7 No, the correct answer istrue4.  In a local area network, several computers can communicate and share data.  Do you want another question?S _ "_ 7 F #F 7 True or False?N The speed of transmission of analog signals is measured in bits per second.S `  a > Sorry, but that was a difficult question.  The statement is	<false.
CDigitalO transmission, not analog transmission, is measured in bits per second or the
 baud rate.& This ends the questions for Unit 2.S F #F 7	    Very good, the statement is	false.)$Digital transmission speed, not analogH transmission speed, is measured in bits per second, or the baud rate.& This ends the questions for Unit 2.S F #F 7	   %&tĿ&t'             4t&t'             4t		&t 	(pMULTIPLEXER	3 	4t

&t 
(            
4t
5&t (            4t&t
%" This part of Lesson 3 describes multiplexing,".a way of carrying more than one* signal over a single transmission path.S 0 	 % 	   @  %    P5 	 ? 	      %    c 2	   '(H $ooͿ8H H &oo78H H &oo	,LESSON4378H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2378H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 3, Unit 3.  After you have finished reading2 this material, press the space bar to continue.S d #d 5	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S e !e 5 h #h 7  0 
5 NSince it is expensive to build transmission systems, it is desirable to use4each physical link to its maximum capacity.  With6multiplexingB, severalN	signals are combined so that they can be transmitted together over a single*physical link, such as a wire or cable. HDifferent techniques are usually used to multiplex analog and digitalJchannels.  Frequency division multiplexing (FDM) is most often used forManalog channels.  For digital signals, time division multiplexing (TDM) ismost common.' Do you want to review more material?S f 2 d #d 5 With"	frequency division multiplexing)(, several signals may be sent together?over one transmission channel by altering their frequencies.
 L
With frequency division multiplexing, a single pair of wires can transmitK12 conversations instead of one, and larger cables or radio channels canGsimultaneously transmit hundreds or even thousands of conversations.' Do you want to review more material?S g 7 d #d 5 NFor digital transmission channels, a different technique is generally used.Intime division multiplexing0!, several messages may be sent simultaneouslyM	on a single transmission channel by altering the time span over which theyare sent. MWith time division multiplexing, hundreds or even thousands of digital bitIstreams can be coded on a single channel in an uninterrupted stream of
0s and 1s.# This ends the review for Unit 3.S d #d 5	   R Which type of multiplexing is used most commonly for sending multiple telephoneF conversations or analog signals over a single transmission channel?	 	 A "	Frequency division multiplexing
   B Time division multiplexing
   C Analog division multiplexing S i !i  j !j  k !k 
 That's it."Frequency division multiplexing",is the type of multiplexing forS analog signals, such as voice conversations.  The different voices are raised in= frequency to different levels so they can travel together.  Do you want another question?S l "l 7 d #d 70 That's not right.  Time division multiplexing!.is used to subdivide a digitalMbit stream, while"frequency division multiplexing.is used for analog signals.  Do you want another question?S l "l 7 d #d 7I Not quite.  The type of multiplexing used for analog signals is calledGfrequency division multiplexing,$not analog division multiplexing.  Do you want another question?S l "l 7 d #d 7 True or False?S A digital bit stream can be subdivided to carry lesser bit streams by using time
 division multiplexing.S m !m  n !n  Yes, the correct answer wastrue."Time division multiplexing
=is used toP subdivide a digital bit stream.  For example, every third bit in a high-speed/ bit stream may be a bit from one subchannel.  Do you want another question?S o "o 7 d #d 7S That's not right.  Time division multiplexing is used to subdivide a digital bit* stream; frequency division multiplexing&(is used for sending multiple analog signals.  Do you want another question?S o "o 7 d #d 7 True or False?O If a transmission path is carrying three telephone conversations at the same$
 time, multiplexing has been used.S p  q  You're right, it'strue8that if several messages are being sent over the sameL pair of wires, multiplexing is necessary so that the conversations do not interfere with each other.& This ends the questions for Unit 3.S d #d 7	    That is incorrect.  It istrue4that without multiplexing the three conversationsP would interfere with each other.  By using this technique a transmission path0 can carry a number of calls at the same time.& This ends the questions for Unit 3.S d #d 7	   
''
%,,,, ' ,,,,',,,   ,, ' ,,(),+'-,,,.....5	8>?		'''	(	6	=_	>

(
3___
6(	"______(
	____________O This part of Lesson 3 describes several types of wire and cable distribution# systems and discusses their use.S s 2	   '(H $ooͿ8H H &oo78H H &oo	,LESSON4378H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2478H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 3, Unit 4.  After you have finished reading2 this material, press the space bar to continue.S t #t 5	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S u !u 5 x 2  0 
5 OThe U.S. National Network includes a number of transmission media, includingGopen-wire pairs, wire-pair cables, coaxial cable, fiber-optic cable,<	microwave radio transmission, and satellite transmission. HA single message often passes through a number of transmission media.' Do you want to review more material?S v 2 t #t 5 IA century ago, the majority of telephone connectors were made by meansofopen-wire pairs;stretched between strings of telephone poles.  Open-wireLpairs have now been replaced in most cities but are still seen frequently2in rural areas and in less-developed countries.
 
Wire-pair cables>
consist of as many as several hundred pairs of wire twistedOtogether within a single protective sheath.  The fact that wires are bunched2tightly together makes them more susceptible to4crosstalk=, a type ofD
electrical interference which causes a telephone user to hear the:conversations of others very faintly in the background.' Do you want to review more material?S w 7 t #t 5 Coaxial cable?consists of a hollow cylinder, usually copper, surrounding aOsingle wire conductor. A much larger number of channels can be sent over oneK	coaxial cable than a wire-pair cable of the same size, and the amount ofcrosstalk is negligible. Fiber-optic cable7uses flexible, extremely small glass fibers to carryGdigital pulses of light.  The advantages of this medium include high9transmission quality and very high capacity and speed.# This ends the review for Unit 4.S t #t 5	   , Open-wire pairs are most appropriate for:  A Computer data transmission	   B Voice transmission   C *High-speed or high-volume transmissions S y !y  z !z  { !{ K That's not it.  This type of distribution system is most appropriate forIvoice transmission.  Do you want another question?S | #| 7 t #t 7: That's right.  Open-wire pairs are most appropriate for8voice and low-data transmissionD
needs.  That's one reason why they are still seen in rural areas, but not in most cities.  Do you want another question?S | #| 7 t #t 7L That's not right.  Wire systems for high-speed data transmission are veryG expensive.  This type of distribution system is most appropriate forEvoice and low-data transmission	needs.  Do you want another question?S | #| 7 t #t 7R Which distribution system is playing an increasingly important role as a result. of its high transmission quality and speed?	 	 A 	Open-wire pairs
   B Coaxial cable
   C Fiber-optic cable S } !}  ~ !~   ! O Sorry.  Open-wire pairs are now being phased out due to their relatively low9 transmission quality and speed.  The correct answer is7fiber-optic cable.  Do you want another question?S  " 7 t #t 7O Sorry.  While coaxial cable has a higher transmission quality and speed than- open-wire pairs, it is not as efficient as+fiber-optic cable.  Do you want another question?S  " 7 t #t 7) That's right.  An increasing number of'fiber-optic cables:are being used as their cost comes down.  Do you want another question?S  " 7 t #t 7 True or False?Q Right-of-way is a far more important issue for a fiber-optic system than it is
 for open-wire pairs.S  !   !  Sorry, that statement is	false.&!A telephone company must obtain theR right-of-way between any two points it wishes to connect by wire or cable.  The: specific type of wire or cable is generally irrelevant.  Do you want another question?S  # 7 t #t 7 Correct, that statement is	false.&"A telephone company must obtain theR right-of-way between any two points it wishes to connect by wire or cable.  The: specific type of wire or cable is generally irrelevant.  Do you want another question?S  # 7 t #t 7K If you are talking on the phone and you hear another conversation in theQ background, which transmission medium is most likely being used for your call?	 	 A 	Wire-pair cables
   B Coaxial cable
   C Fiber-optic cable S  !   !   ! S That's right.  The fact that wires are bunched together so tightly increases the likelihood of crosstalk inwire-pair cables.  Do you want another question?S  # 7 t #t 7N Sorry.  The design of coaxial cable minimizes the possibility of crosstalk. However, the fact thatwire-pair cables+(pack the wires so tightly together leads= to a higher risk of faint conversations in the background.  Do you want another question?S  # 7 t #t 7P Sorry. Fiber-optic cables use digital transmission techniques which eliminateC the possibility of crosstalk.  This phenomenon is most likely inAwire-pair
 cables.  Do you want another question?S  # 7 t #t 7O Which distribution system consists of a hollow copper cylinder surrounding a single-wire conductor?	 	 A 	Open-wire pair
   B Wire-pair cable
   C Coaxial cable S  !   !   ! " That's not it.  Open-wire pairs0 refer to pairs of copper wires suspended fromR insulators located on the crossbars of poles.  The above definition refers to a coaxial cable.  Do you want another question?S  # 7 t #t 7 Not quite.  Wire-pair cables5are made of insulated conductors which are brought' close together and twisted in pairs.&Coaxial cables,6the correct answer, have a' single-wire conductor in a cylinder.  Do you want another question?S  # 7 t #t 70 That is correct.  This is the definition of a.coaxial cable.>These cables have5 been installed as inner city trunks in many areas.  Do you want another question?S  # 7 t #t 71 Which statement regarding fiber-optic cable is	/false?  A %They are made primarily of copper.	   B ,They use laser light to transmit signals.   C ?They are smaller than coaxial cables and twisted wire pairs. S       Good.  Fiber-optic cablesarenot
"made of	*copper 0.  They are glass fibers made% from a limitless resource -- sand.& This ends the questions for Unit 4.S t #t 7	    No.  Fiber-optic cables do4use laser light since lasers provide a narrow and# intense beam of light.  They are!not%however, made of
6copper.& This ends the questions for Unit 4.S t #t 7	    Sorry.  Fiber-optic cables7are indeed smaller than these other types of cables.G In fact, they are only slightly wider in diameter than a human hair.FThey are not, however, made of
copper.& This ends the questions for Unit 4.S t #t 7	    True or False?Q The major advantages of fiber-optic cable include the ease of construction and=
 reduced cost compared to other cable distribution systems.S     Incorrect.  This is afalse-statement about fiber-optic cables.  Their construction is timeconsuming, and costs are.quite high.  These are9 disadvantages, rather than advantages, of this system.& This ends the questions for Unit 4.S t #t 7	    Good.  This is afalse<statement about fiber-optic cables.  The major advantagesO of this system is its high transmission quality.  It is, however, costly and time consuming to construct.& This ends the questions for Unit 4.S t #t 7	   9____0[][]____(=)____[][]0[][]	8(____)B[][]	__	____/
[
HI!
][[__	__][_//\/\
/\
/\
/\/\/\/\//!\//\	\
/\/\/\///"\//\/
/\\/\/#\P This part of Lesson 3 describes microwave and satellite distribution systems,( including how and where each is used.S   
[
 aaaaaaaa
HI!S   
 aaaaaaaa
HI!S   $!	 I
 aaaaaaaa
HS   .!)I$H	  a
 aS   . a) aF a$ aIH	MIS   F aI a	M aS  2	   '(H $ooͿ8H H &oo78H H &oo	,LESSON4378H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2578H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 3, Unit 5.  After you have finished reading2 this material, press the space bar to continue.S  # 5	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S  ! 5  # 2  0 
5 Microwave transmission5is a distribution system that uses microwave radioLsignals.  Calls are sent via conventional methods to a microwave station.
 O
At a microwave station, an antenna transmits the signal through the air to areceiving antenna. IThe two antennas can be as much as 30 miles apart.  If the distance is;greater than 30 miles, intervening stations may be used.' Do you want to review more material?S  2  # 5 Some
advantages!of microwave transmission are: 5It is a cost-saving means of transmitting signals.
 ;
It is useful where right-of-way requirements are strict.
 A major
limitationis: GThe sending and receiving antennas must be placed in a line-of-sightrelationship to one another.' Do you want to review more material?S  2  # 5    Satellite transmission2is a system which uses a satellite orbiting the1earth to send information over long distances.
 L
A satellite station converts the voice signals to a much higher frequencyJand then transmits them to a satellite.  The satellite sends the signalLdown to another station which then converts it back to the original voice
signal.' Do you want to review more material?S  7  # 5 The
advantages%of satellite transmission include: JSatellite relays can be less expensive than running cable or building a,
large number of microwave relay stations.
 H
Remote areas can be reached using this distribution system which werepreviously not accessible.# This ends the review for Unit 5.S  # 5	   R Which of the following is a major limitation of microwave transmission systems?  A Right-of-way requirements	   B Line-of-sight requirements   C Excessive cost S  !   !   ! Q That's incorrect.  Microwave is particularly suited to areas with right-of-way- restrictions, so this is not a limitation.,Line-of-sight:requirements are," however, a major consideration.  Do you want another question?S  " 7  # 7  That's right.  The need for aline-of-sight',relationship between the sending andF receiving antennas is a major limitation of microwave transmission.  Do you want another question?S  " 7  # 7P That's not it.  Microwave transmission is a cost-saving means of transmitting signals, but
line-of-sightrequirements(are a limitation.  Do you want another question?S  " 7  # 7 True or False?S In a microwave distribution system, the sending and receiving antennas can be as
 much as 100 miles apart.S  !   ! : That's not right.  The two antennas can be no more than830 milesAapart.  If theR distance to be covered is greater than 30 miles, intervening microwave stations are needed.  Do you want another question?S  " 7  # 7 You're right, it'sfalse:.  If the antennas were 100 miles apart, an interveningC microwave station would be needed.  The two antennas can only beA30 miles	Japart.  Do you want another question?S  " 7  # 7 True or False?P In a microwave transmission system the sending and receiving antennas must be$
 free of intervening obstructions.S  !   !  That's right, it'strue./The two antennas must be free of interveningM obstructions.  They must have what is called a line-of-sight relationship.  Do you want another question?S  # 7  # 7
 No.  It istrue6that the sending and receiving antennas must have aQ line-of-sight relationship, which means there are no intervening obstructions.  Do you want another question?S  # 7  # 7P Which telephone distribution system is probably most appropriate for a remote and inaccessible area?	 	 A 	Coaxial cable
   B Satellite transmission
   C Microwave transmission S      L No.  It would be very difficult to lay cable to a remote and inaccessible location.Satellite transmission,"would be much cheaper and more practical.& This ends the questions for Unit 5.S  # 7	    That's right.Satellite transmission*&is ideal for inaccessible areas, and isR often cheaper than building microwave relay stations even if they are feasible.& This ends the questions for Unit 5.S  # 7	   Q Not quite.  Microwave transmission would require building relay stations everyL 30 miles or so, which could be expensive and impractical for inaccessible! locations.  A better choice issatellite transmission.& This ends the questions for Unit 5.S  # 7	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^O Now you can try applying the material in Lesson 3.  Your task is to design aR telephone distribution system for the island of Batwini and its capital city of Danimia.S  $ 5	   O To successfully complete this exercise you will need to be familiar with the( basic concepts explained in Lesson 3. Would you like to:  A Go on to the exercise   B "Review the material in Lesson 3 S  5  0 
5R In this exercise you will be asked to face a rather unique challenge.  You mustQ design a distribution system for an island that currently has no telephones at	 all. Batwini was discovered3in the Bermuda Triangle in the late 1980s.  As aO technical advisor to the newly formed Batwini Telephone Company, you will beQ asked to evaluate the best way to connect potential subscribers to the capitalM city of Danimia.  In each case, you will be asked to choose a distributionQ system: open-wire pairs, coaxial cable, fiber-optic cable, microwave radio, or
 satellite.S  2	   R The first subscriber is a private residence in a sparsely populated rural area.L The residence is separated from the capital city by 10 miles of farmland.S    H.	/~\G../\?
ͻ ,?ڿ""!"#Ŀ)пAĴ		!..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^S  3	  R The second area to be connected is the smaller city of Prada which is separated< from the capital by a nearly impassable canyon and river.S    H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   
Ŀ
ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵ .".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^S  3	  P The third is the island of Bosa, located 250 miles away from the main island.S    H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/
\/\

!

#Danimia
-                      //\ !A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^S  3	  S The fourth user is an oil company research installation on the shore of the mainN island; its minicomputers must be connected to the mainframe in the capital city.S    H.	/~\G../\?ͻ,1?2ڿ""!Ŀ),-AĴ'	                    ..  /\..	,.	-	A	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^S  3	  L The fifth area to be connected to Danimia is a forest ranger station in a national wildlife preserve.S    H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-

6^     ^Ĵ?͵.".#.%.&'..)*.+.,.-/?0/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^S  3	  S The final subscriber is the Club Batwini Resort, currently under construction onA the beachfront approximately five miles from downtown Danimia.S    H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-
D//      \,-A(_/_)~~ ~ ~~~~~ ~~?ͼ,1?2C
~~~~~ ~~~~B^S  , 5	  < Which telephone subscriber would you like to connect now?  A The private residence&' E -The forest ranger station	 	&  B The city of Prada&'x (F -The Club Batwini Resort &  C The island of Bosa&' G -Press G when finished &  D The research installation S  5  5  5  5  5  5  ! 5H.	/~\G../\?
ͻ ,?ڿ""!"#Ŀ)пAĴ		!..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^P You have chosen the private residence and must now decide how to connect this subscriber to Danimia.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7S Only voice data will be transmitted from this residence telephone.  There are no+ other subscribers in the immediate area.I Would you like more information before choosing a distribution system?S  # 7  - 5R There are no right-of-way requirements in this part of Batwini.  The terrain is# fairly flat and the land is dry.F Do you want more information before choosing a distribution system?S  # 7  - 5H The residence is located in a sparsely populated, rural area which is economically depressed.F Do you want more information before choosing a distribution system?S  # 7  - 5O Which distribution system would be best for connecting this residence to the capital city?	 	 A 	A satellite link	'	( C 	.Open-wire pairs
 
'  B Fiber-optic cable'( D .Microwave radio
 
'S      7  R That is incorrect.  A satellite link would be far too expensive for this singleF subscriber, and it is also unnecessary for such a short connection.S  $ 7	   Q That is not the best choice.  Fiber-optic cable is too expensive for this typeG of connection.  Also, it is not required for the needs of this user.S  $ 7	   L Not quite.  Microwave radio is not needed for this connection.  There areJnoR right-of-way requirements in this area, and the distance to Danimia is only ten	 miles.S  $ 7	    Do you want to:  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7	ĿĿ		..  /\..	.		>/~\
Ĵ.
.
Ĵ
..
..
.

=/  \.
..
......
</_____\.	
........<B

	

Danimia
0
   $(,048
<
;Home Sweet>HomeQ Good.  Open-wire pairs are the best choice since it is a single residence in aR sparsely populated area.  There are no right-of-way requirements, and cost is a
 factor.S  , 7	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   
Ŀ
ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵ .".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^Q Now you need to decide how to connect the smaller city of Prada to the capital city of Danimia.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7P Only voice data will be transmitted; there is virtually no industry in Prada.S	 There are approximately 2000 households in Prada which will need to be connected to Danimia.F Do you want more information before choosing a distribution system?S  # 7  - 5K Line-of-sight requirements are not an issue as there are no mountains orS skyscrapers between Prada and Danimia.  There is, however, the Urdi River CanyonQ	 and a 2000 foot gorge between the two cities.  They are approximately 15 miles	 apart.F Do you want more information before choosing a distribution system?S  # 7  - 5R The government of Batwini is committed to the idea of linking the two cities as soon as possible.:
 Of course, cost is a factor for this developing island.F Do you want more information before choosing a distribution system?S  # 7  - 5L Which distribution system would be best for connecting Prada and Danimia?  A A satellite link'( C .Coaxial Cable	 	'  B Fiber-optic cable'( D .Microwave radio 'S        7N Not quite.  A satellite link would be very expensive, and there is a better% choice which would be less costly.S  $ 7	   J That is incorrect.  Fiber-optic cable is very expensive and it would be> impossible to lay this type of cable over the river canyon.S  $ 7	   L That's not it.  Coaxial cable does not suit the terrain between Prada and& Danimia.  There is a better choice.S  $ 7	    Do you want to:  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7___@___(3. . . . . . . . . . . . . . . . . . . . . . .  )(___@___)	Ŀ/\A/\		..  /\..	.		?/\/\
Ĵ.
.
Ĵ
..
..
.

? ..
..
......<Ĵ...	
........<....

	

Danimia

<.Prada' Ŀ'<D#'#'S Right.  Microwave radio is the best choice since the two cities are separated byS the Urdi River Canyon but are only 15 miles apart.  This would be the most cost- effective solution.S  , 7	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/
\/\

!

#Danimia
-                      //\ !A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^Q Now you need to choose the distribution system which is best suited to connect- Danimia on Batwini and the island of Bosa.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7R Both voice and data will be transmitted from the capital to the island of Bosa.K A number of residence telephones will be installed as will branch office	 telephones.F Do you want more information before choosing a distribution system?S  # 7  - 5D Neither right of way nor line-of-sight requirements are an issue.C Between Danimia and Bosa lies 250 miles of rough Atlantic Ocean.F Do you want more information before choosing a distribution system?S  # 7  - 5P No tourism can be developed on Bosa until the island is connected to the mainJ island of Bugundi and the travel representatives in Danimia.  Thus, theK	 government views this connection as critical for future economic growth.F Do you want more information before choosing a distribution system?S  # 7  - 5K Which distribution system would be best for connecting Bosa and Danimia?  A A satellite link'( C .Open-wire pairs	 	'  B Fiber-optic cable'( D .Microwave radio 'S  7      O That's possible.  Although fiber-optic cable can be expensive, it's becomingS more and more cost effective.  But there is another practical solution.  Can you find it?S  $ 7	   N That's not it.  Open-wire pairs might be suitable for connecting individualQ residences on Bosa, but they are not suitable for connecting two islands which are 250 miles apart.S  $ 7	   Q That is not really correct.  Microwave signals would need relays approximatelyQ every 30 miles.  Many of these would be needed since the islands are 250 miles& apart.  There is a better solution.S  $ 7	    Do you want to:  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7*____"[][]___[.]___[][]![][]	)[____]2[][]:		@

>Ŀ
C)
FĿ(	>.. D^EĴ..I.J/\^<Ĵ.@.AĴD..F..I.J
/\_/
\/
\
<.
?.
@.
B.
C
D..
F
G.
H.
I.
J_/\_<=.>?.@......._/Bosa\<>
@DanimiaJ~~~~~~~~~~~~~~~<R Good.  A satellite link is the best choice since Bosa and Danimia are separated by 250 miles of ocean.S  , 7	   H.	/~\G../\?ͻ,1?2ڿ""!Ŀ),-AĴ'	                    ..  /\..	,.	-	A	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^O Now you need to connect the Kolby oil company research installation with the- company's main computer center in Danimia.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7K A great deal of data must be transmitted between the installation's manyM minicomputers and the mainframe, located several miles away in the capital	 city.F Do you want more information before choosing a distribution system?S  # 7  - 5O Right-of-way restrictions are not a problem in that the oil company owns theK land between the research installation and the company's headquarters in	 Danimia.F Do you want more information before choosing a distribution system?S  # 7  - 5R Kolby Co. is the wealthiest company in Bugundi.  They have specified a need forF high-capacity equipment and consider cost to be a secondary factor.F Do you want more information before choosing a distribution system?S  # 7  - 5N Which distribution system would be best for connecting Kolby Co.'s research; installation with the company's headquarters in Danimia?	 	 A 	A satellite link	&	' C 	-Open-wire pairs
 
&  B Fiber-optic cable&' D -Microwave radio
 
&S    7    R That is incorrect.  The research installation is only a few miles from Danimia,C so a satellite link is not necessary.  There is a better choice.S  $ 7	   P That's not it.  A great deal of data must be transmitted, and open-wire pairs& could not meet the company's needs.S  $ 7	   M Not quite.  As there are no right-of-way restrictions between the research8 installation and Danimia, there is a better solution.S  $ 7	    Do you want to:  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7I.H.F..	ĿĿE...		..  /\..	.		DĿ.
Ĵ.
.
Ĵ
..
..
.

D
Fÿ.
..
......>___DF.	
........=(___)ĴF

	

Danimia

=OIL
D
F=2fiber-optic cableS Yes.  Fiber-optic cable is the best choice since the research installation needsL to rapidly transmit a large amount of data to the company headquarters inQ Danimia.  Since there are no right-of-way restrictions and cost is a secondary# factor, this is the best choice.S  , 7	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-

6^     ^Ĵ?͵.".#.%.&'..)*.+.,.-/?0/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~?ͼ,? 
~~~~~ ~~~~B^K Now you need to connect the forest ranger station, located in a wildlifeH preserve, to the weather bureau and park service building in Danimia.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7M Both voice and weather data will be transmitted to Danimia from the ranger2 station located approximately seven miles away.F Do you want more information before choosing a distribution system?S  # 7  - 5K Right-of-way restrictions are a problem since the natural terrain of theL preserve must be maintained.  Line-of-sight is not an issue as the rangerN	 station is seven miles due east of Danimia and that area of the preserve is primarily flat marshland.L Do you want additional information before choosing a distribution system?S  # 7  - 5L The park department of Batwini has a limited budget, so cost is a factor.S However, the preservation of the natural terrain and wildlife breeding ground is!	 a more critical consideration.F Do you want more information before choosing a distribution system?S  # 7  - 5S Which distribution system would be best for connecting the ranger station to the& weather/park department in Danimia?	 	 A 	A satellite link	&	' C 	-Open-wire pairs
 
&  B Fiber-optic cable&' D -Microwave radio
 
&S        7R Not quite.  The ranger station is only seven miles from Danimia, so a satellite: link would not be necessary.  There is a better choice.S  $ 7	   P That is incorrect.  There are strict right-of-way limitations on the wildlifeR preserve, thus the fiber-optic cable would not be feasible.  Cost would also be prohibitive.S  $ 7	   Q That is incorrect.  Open-wire pairs would not be the correct choice because of@ the strict right-of-way limitations on the wildlife preserve.S  $ 7	    Do you want to  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7___9___/( .   .   .   .   .   .   .   .   .   .   .)(___9___)	Ŀ/\Ŀ:/\F^		..  /\..	.		7ͻ	E/\
Ĵ.
.
Ĵ
..
..
.

7
:   
D/\/\.
..
......7	9/\  D//\\.	
........7ͼ
C/\/\/\

	

Danimia

:      ////\\\\:F
6Ranger DanR Good.  Microwave is the best choice due to the strict right-of-way limitations.0 Cost also makes microwave a desirable choice.S  , 7	   H.	/~\G../\?ͻ ,?ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ?͵.".#.%.&'..)*.+.,.-?/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-
D//      \,-A(_/_)~~ ~ ~~~~~ ~~?ͼ,1?2C
~~~~~ ~~~~B^R Now you need to connect the new beachfront resort, Club Batwini, to the capital city of Danimia.S  # 7	   = Your choice of a distribution system may be influenced by:  A 'User needs (type of data being sent)	   B .Right-of-way and line-of-sight requirements   C Economic factors + Which would you like to know more about?S  ! 7  ! 7  ! 7O Only voice data will be transmitted from the Club Batwini Resort to Danimia.M Private telephones will be installed in each of the 2000 condominium units!	 planned for this plush resort.F Do you want more information before choosing a distribution system?S  # 7  - 5K Right-of-way has already been granted by the Danimia board of selectmen.N Line-of-sight is problematic due to the other high rise hotels in the area.L Do you want additional information before choosing a distribution system?S  # 7  - 5P The budget for this project is fixed; the developer wants the most economicalR system.  Of course, since it will be an exclusive resort, the developer is also,	 concerned with the "looks" of the system.F Do you want more information before choosing a distribution system?S  # 7  - 5Q Which distribution system would be best for connecting the Club Batwini Resort with the capital city?	 	 A 	Open-wire pairs	%	& C 	,Coaxial cable
 
%  B Fiber-optic cable%& D ,A satellite link
 
%S      7  Q This is incorrect.  The Club Batwini is being built as a luxury island resort,K so stringing wires for each telephone would not be a good choice for the image-conscious developer.S  $ 7	   M Sorry.  The transmission needs of the resort would not warrant fiber-opticI cable, and the cost would be excessive to the budget-minded developer.S  $ 7	   O That is incorrect.  A satellite link is not necessary for this user, and the cost would be far too great.S  $ 7	    Do you want to  A Learn more about the problem	   B )Choose a different distribution system S  # 5  - 7	ĿĿ		..  /\..	.	
Ĵ.
.
Ĵ
..
..
.

8________.
..
......
7/////\\\\\.	
........
7Bugundi 

	

Danimia

7____>B\_/Coaxial CableD\~~S Right!  Coaxial cable is the best choice for the Club Batwini.  Right-of-way hasO already been approved so underground cables are not a problem, and the price is right.S  , 7	   N Have you completed the external wiring of all six users to the capital city of Danimia?S 7  2M Most people find they learn this material best if they complete all of the0 examples.  Are you sure you have seen enough?S  7  , 5H.	/~\G../\ͻ ,ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ͵.".#.%.&'..)*.+.,.-/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~ͼ, B^H If you connected all six users to Danimia, then you have successfully "put it all together!"S 3	   S But suppose some users don't want to talk to Danimia.  Suppose they want to talk to each other.S 2	  H.	/~\G../\Gڿ""!Ŀ)ĿAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^
Ĵͻ.".#.%.&'..)*.+.,.-5/|\/\ /|\	/\   .!".#.......5/|\/\ /|\
/  \/\ ͼ    
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~CB^G Imagine if it was also necessary to connect the city of Prada to the Island of Bosa...S 3	  @ ...the Club Batwini to the Kolby Co. research installation...S   H.	/~\G../\Gڿ""!Ŀ)Ŀ
AĴͻ'	                    ..  /\..	,.	-                   	J	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^
J
Ĵͻ.".#.%.&'..)*.+.,.-5/|\/\ /|\J	/\   .!".#.......5/|\/\ /|\J
/  \/\ ͼ    
!

#Danimia
-                      /
J/      \A(_/_)J~~ ~ ~~~~~ ~~CͼB^S 3	  J ...the island of Bosa to the ranger station on the wildlife preserve...S   H.	/~\G../\Gڿ""!Ŀ)Ŀ
AĴͻ'	                    ..  /\..	,.	-                   	J	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^
J
Ĵͻ.".#.%.&'..)*.+.,.-5/|\/\ /|\J	/\   .!".#.......5/|\/\ /|\J
/  \/\ ͼ    
!

#Danimia
-                     /
J/      \ͻ8A(_/_)J~~ ~ ~~~~~ ~~8Cͼ ͼB^S 3	  C ...and the city of Prada to the Kolby Co. research installation.S 	  H.	/~\G../\4ͻGڿ""!Ŀ)Ŀ
AĴͻ'	                   ..  /\..	,.	-                   	J	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^
J
Ĵͻ.".#.%.&'..)*.+.,.-5/|\/\ /|\J	/\   .!".#.......5/|\/\ /|\J
/  \/\ ͼ    
!

#Danimia
-                     /
J/      \ͻ8A(_/_)J~~ ~ ~~~~~ ~~8Cͼ ͼB^S 
3	  P Obviously a system which directly connected every possible pair of telephones& would be confusing and inefficient.S   ?
ͻH.	/~\0
ͻEG../\4ͻEGڿͳ""ͻ    !Ŀ)Ŀ9
AĴͻ	'	                  ..  /\..	,.	-                  	J



   Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
9  ^
D
J	    ͳ
Ĵͻ.".#.%.&'..)*.+.,.-5/|\/\ /|\ͼJͼ   /\   .!".#.......5/|\/\ /|\J 
    /  \/\ ͼ    
!

#Danimia
-                   /
J   /      \ͻ8<A(_/_)J ~~ ~ ~~~~~ ~~!ͼ<ͳͼ:ͼB^S 2	  H.	/~\G../\ͻ ,ڿ""!Ŀ)пAĴ'	                    ..  /\..	,.	-                   	
Ŀ ڿ
Ĵ.
#.
$Ĵ
'..
)..
,.
-
6^
<^Ĵ͵.".#.%.&'..)*.+.,.-/|\/\ /|\	/\	 .!".#.......5/|\/\ /|\
/  \/\                 
!

#Danimia
-                      //      \A(_/_)~~ ~ ~~~~~ ~~ͼ
#Central, 	#OfficeB^S Lesson 4 will show you how networks and central offices produce a more efficient telephone system.S  0 
5	    O  ͻ  J 	LESSON 3  O   ͼ   O       	Unit MenuS   J 	LESSON 3    	Unit 1 - Voice CommunicationsS   O  ͻ  J 	LESSON 3  O   ͼ   O        	Unit 1 - Voice CommunicationsS   G  J 	LESSON 3  G p()G  @	G   	Unit 1 - Voice CommunicationsS   J 	LESSON 3   	Unit 2 - Data CommunicationsS   O  ͻ  J 	LESSON 3  O   ͼ   O       	Unit 2 - Data CommunicationsS   G    J 	LESSON 3  G  pG   G 	t    G 	Unit 2 - Data CommunicationsS   J 	LESSON 3   	Unit 3 - MultiplexingS   O  ͻ  J 	LESSON 3  O   ͼ   O       	Unit 3 - MultiplexingS   G L OM L O   J 	LESSON 3  HLOULO @LOXLO   	Unit 3 - MultiplexingS   J 	LESSON 3   /	Unit 4 - Wire and Cable Distribution SystemsS   O  ͻ  J 	LESSON 3  O   ͼ   O       /	Unit 4 - Wire and Cable Distribution SystemsS   @    J 	LESSON 3  @     @     /	Unit 4 - Wire and Cable Distribution SystemsS   J 	LESSON 3   8	Unit 5 - Microwave and Satellite Distribution SystemsS   O  ͻ  J 	LESSON 3  O   ͼ   O       8	Unit 5 - Microwave and Satellite Distribution SystemsS   @   G O)J 	LESSON 3  @  GO) @ ص   8	Unit 5 - Microwave and Satellite Distribution SystemsS   J 	LESSON 3   #	Unit 6 - Putting It All TogetherS   O  ͻ  J 	LESSON 3  O   ͼ   O       #	Unit 6 - Putting It All TogetherS   Oڿ ĿJ 	LESSON 3  Oͳ^  O#	Unit 6 - Putting It All TogetherS GF @CG D@PressIG 	J@space S !D @AG 	B@SelectHG I@YJG K@orMG N@N S "D @AG 	B@SelectHG I@TJG K@orMG N@FOG S #S @ Select A-C S $D @AG 	B@SelectHG I@AJG K@orMG N@BOG S %G @DG 	E@SelectKG L@1-3 S &G @DG 	E@SelectKG L@1-4OG S 'G @DG 	E@SelectKG L@1-5OG S (G @DG 	E@SelectKG L@1-6OG S )G @DG 	E@SelectKG L@1-7OG S *G @DG 	E@SelectKG L@1-8OG S +G @DG 	E@SelectKG L@1-9OG S ,G @DG 	E@SelectKG L@A-GOG S -G @DG 	E@SelectKG L@A-DOG S .G @DG 	E@SelectKG L@A-EOG S /G @DG 	E@SelectKG L@A-F S 0G @DG 	E@SelectKG L@A-HOG S 1S 2S 3S 4S 5S 6S 7S 8S  @ @ @ @ 
@ @ @ @ @ @ @ @ @ @ @  @ "@ $@ &@ (@ *@ ,@ $-O                                 @ @ @ @ 
@ @ @ @ @ @ @ @ @ @ @  @ "@ $@ &@ (@ *@ ,@ $-O LESSON 4 - MAKING A CONNECTION  	@ 	@ 	@ 	@ 	
@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	@ 	 @ 	"@ 	$@ 	&@ 	(@ 	*@ 	,@ $	-O                                 
@
@
@
@

@
@
@
@
@
@
@
@
@
@
@
 @
"@
$@
&@
(@
*@%
,@S iciGl   J 	LESSON 4   	IntroductionS ;> = < ; This lesson will introduce: $The mechanics of a telephone callS ?n	  W This lesson will introduce: $The mechanics of a telephone call*
    The functions of the central officeS = This lesson will introduce: $The mechanics of a telephone call
 &
The functions of the central office     The U.S. National NetworkS > This lesson will introduce:(    The mechanics of a telephone call*
    The functions of the central office     The U.S. National NetworkS ?
	
p
	

 aaaaaaaaaaaaaaaaaaaaaaa  
 aaaaaaaaaaaaaaaaaaaaa		 aaaaaaaaaaaaaaaaaaaaaaaaa
  


 aaaaa





Ŀ
  aaaaa
=Ŀ	
p 
 aaaaa
p       =Central	
p
 aaaaa=Office 
ͻ





 
 _____________________________
=
EȻ"5=EȻͱp!=E =Q More specifically, you will learn about the steps involved in making a typical telephone call...S @ 
" aaaa05S A  " a0 a>5S B  
"5>5S C  
" a05>5S D  " a0 a>55S E  
"5>55S F  
" a05>55S G  " a0 a>555S H  "7>555S I  " a07>555S J  " a0 a>5557S K  
"4>5557S L  
" a04>5557S M  " a0 a>55574S N  "8>55574S O  " a08>55574S P  " a0 a	>555748S Q  "3	>555748S R  " a03	>555748S S  " a0 a
>5557483S Tn	  Wܱ
Ŀ߱!!	Ȼ						
Ȼ






4Ȼ.@Ȼٱ.@    3G__6@    


 

"
)
.@
/G___
:@
;.@  
1Gswitch 8@  .@
.Central	6OfficeN ... and the switches which allow the central office to connect your call to another subscriber.S U 
 	
(S V .@    3L_4G5O 6@    
 
,
/
3L_/
5O 
6G
:@
;.@  	1Lswitch7G 8@  S W 
4
7	.@4	5@.@    4̺6@    
)
.@
/G
6G
:@
;S X 
4
6
>/@/@    3G__6@    
/G___
:@
;/@  
1Gswitch 8@  S Y 
4

@S Z 
4S [n	  W;<p  >߱9:p    	t*.p
/        9p   <*p  p                        /0p  2 5p        =		p 	t*		p                        	/t*	0p         	9 	:p 	;t*	<p

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    R You will also learn about the many possible paths which link telephone users in the U.S. National Network...S \ ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        *	0	;p*

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S ] ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p            	#         	,	/p*	0	;p*

p  

p          *
"
-p          
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S ^ ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p            	#         	,	/p*	0	;p*

p  
	
p      

!p*
"
-p          
7 
8t  
:pp     p                            : p    p                 /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S _ ;<p  >߱9:p    	t*.p
/        9p   <*p  p                        /0p  2 5p        =		p 	t*		p                        	/t*	0p         	9 	:p 	;t*	<p

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S ` ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*	0p         	9 	:p *

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S a ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*
	0p       	7	;p*

p  

p          
!t*
"p                     
7
8t  
:p"p                               78p  : p                      /t 0p*
18

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S b ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*
	0p       	7	;p*

p  

p          
!t*
"p                     
7
8t  
:p"p                               78p  : p           $0p*
18

p  
*


%p   
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S cn	  W``	 O      &@   )O         2
@ O   #@   &O            23	
``		@   	#O               	2

@
 O  Central Office  
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@L ... and how calls may sometimes be blocked if there is too much telephone traffic.S d `` Lͻ   2
@ O   #@   &O        .L23	
``		@   	#O               	2

@
 O  Central Office  
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@S e `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@S f `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ Lͻ%O   (@  *O        2
@ O    $L23

``

@
 O   
#@  
%O 
&@ 
'O   
*L 

+O       
2@@S g `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ Lͻ%O   (@  *O        2
@ O    $L23

``

@
 L

"BLOCKED
)O 
*L 

+O       
2@@S hn	  W	#	%	'	)	+
#
%
'
)
+!
#p       *x+p-!"*x+p-
!
"p        
*x
+_______________"#p     (x+p,-_______________*@<.N After learning this material, you will be asked to "put it all together" byR calling several members of your family to get your Uncle Sid's new phone number( so you can wish him a Happy Birthday.S iciGl	  W6 Please choose the topic you would like to see next:  A Introduction'( E 	.Unit 4	 	'	.Traffic Theory  B 	Unit 1'( F 	.Unit 5 The Steps in a Call'.Putting It All Together  C 	Unit 2'( G .Exit This Lesson Dialing and Switching'  D 	Unit 3 The National NetworkS :l jHl Kl Nl Ql Tl  l
	
p
	

 aaaaaaaaaaaaaaaaaaaaaaa  
 aaaaaaaaaaaaaaaaaaaaa		 aaaaaaaaaaaaaaaaaaaaaaaaa
  


 aaaaa





Ŀ
  aaaaa
=Ŀ	
p 
 aaaaa
p       =Central	
p
 aaaaa=Office 
ͻ





 
 _____________________________
=
EȻ"5=EȻͱp!=E =L This Unit describes the specific steps involved in completing a telephone call.S k 
" aaaa05S l  " a0 a>5S m  
"5>5S n  
" a05>5S o  " a0 a>55S p  
"5>55S q  
" a05>55S r  " a0 a>555S s  "7>555S t  " a07>555S u  " a0 a>5557S v  
"4>5557S w  
" a04>5557S x  " a0 a>55574S y  "8>55574S z  " a08>55574S {  " a0 a	>555748S |  "3	>555748S }  " a03	>555748S ~  " a0 a
>5557483S i	  W'(H $ooͿ8H H &oo78H H &oo	,LESSON4478H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2178H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 4, Unit 1.  After you have finished reading2 this material, press the space bar to continue.S ZIl	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S XJl Zn iciGl NWhen you lift the handset of your telephone to make a call, equipment whichLmay be located miles from your home instantly registers the fact that you5	have begun a call.  This equipment is located at a	7central office	F(CO). Thecentral office;provides local exchange service for a given geographicalarea. The primary function ofthe central office/is to connect you with othertelephone users.' Do you want to review more material?S i ZIl LWhen the handset of your telephone is in the cradle, it holds down one ortwo buttons calledswitchhook buttons.
 H
When these buttons are depressed, your telephone is said to be in theon-hook condition. 	In theon-hook condition,/the electrical current sent from the central5office cannot flow through the switchhook buttons.' Do you want to review more material?S i ZIl 1When you lift the handset, a spring forces the3switchhook buttons
Fup and the$switchhook completes the circuit.
 A
When these buttons are up, your telephone is said to be in the
Coff-hook
condition. 	In theoff-hook condition,/the electrical current sent from the centraloffice flows in the circuit.' Do you want to review more material?S i ZIl LWhen you lift the handset from the cradle, you send an electrical signal,anoff-hook message,:to the central office.  This indicates that you want to	make a telephone call. +The central office responds by sending a-dial tone7to your telephone set.IThis indicates that your central office is ready to accept a telephone
number.'Do you want to review more material?S i ZIl OThe lines between a local subscriber and a local central office are called alocal loop.
 =
All telephones within a local exchange area begin with the
?same 3-digitexchange. Each local exchange controls!up to 9,999 local loops9for a particulargeographic area.' Do you want to review more material?S i ZIl MAfter a connection has been made between two telephones served by the samecentral office, aringing message$&is sent to the line being called.
 
A separate
ring-back message2
!is sent to the caller to let them know that the$line they are calling is ringing. MWhen the person being called removes the handset from the cradle, the loopOto that telephone is complete; when the two telephones are connected in thisway, they are said to be
seized.# This ends the review for Unit 1.S ZIl	  WM Which electronic signal informs the central office that you want to make a telephone call?	 	 A 	The on-hook message
   B The off-hook message
   C The ring-back message S X X XS That's not right.  The on-hook condition means that your handset is on the hook., You need to take it out of the cradle, or*off-hook3to signal that you want to make a call.  Do you want another question?S i Zn Correct.  Theoff-hook message-means you have lifted the handset from the= cradle.  The central office signals back with a dial tone.  Do you want another question?S i ZnP Sorry.  The ring-back message occurs later, after you have dialed the number.8 When you first remove the handset from the cradle, an6off-hook message
Gis sent to the central office.  Do you want another question?S i ZnH Does the central office send an electrical current to your telephone?S  2 That's right.  When your phone is off-hook, the"0circuit is complete and current flows in the circuit.  Do you want another question?S Yn ZnS Incorrect.  An electrical current is normally transmitted through your telephoneQ lines.  When your phone is off-hook, the circuit is complete and current flows in the circuit.  Do you want another question?S Yn Zn True or False?O The lines between a local subscriber and a local central office are called a
 local loop.S X X That's right, it'strue.8The local loop is the link between your telephone and? the local switching equipment located at the central office.  Do you want another question?S Zn Zn No, the correct answer istrue.-!Locally your telephone is connected to the3 central office, and this is called a local loop.  Do you want another question?S Zn Zn? How many telephone numbers can a single local exchange have?  A 9,999	   B 9,999,999   C There is no limit. S X X XQ You're right.  Since all phones in a local exchange share the same three-digitR exchange, only the last four digits in the phone number can change.  Therefore, the maximum number is	9,999.  Do you want another question?S Zn ZnR Incorrect.  There can be up to 9,999,999 different phone numbers within an areaS code.  But within a local exchange, each telephone is identified by a four-digit< number and therefore the maximum number of local loops is	:9,999.  Do you want another question?S Zn ZnO That's not it.  There is a limit to the number of telephone numbers within aS local exchange.  Since the exchange number is the same for each subscriber, onlyQ the last four digits in the phone number can change.  The maximum is therefore	 9,999.  Do you want another question?S Zn ZnP If the telephone you are attempting to call is in the off-hook condition when: you place the call, the central office will send you a:	 	 A 	Ring-back message
   B Busy message
   C Dial tone S   P That's incorrect.  If the phone you were calling was in the on-hook conditionR when you placed the call, the central office would send you a ring-back messageN to indicate that the phone was ringing.  Since the phone is in the off-hook  condition, you will be sent abusy message.& This ends the questions for Unit 1.S Zn	  WN That's right.  When the phone you are attempting to call is in the off-hook( condition, the central office sends a&busy message3to your line.  If the phoneO was on-hook when you placed the call, you would receive a ring-back message.& This ends the questions for Unit 1.S Zn	  WP No.  The central office would have sent you a dial tone before you placed theR call.  In this case, the phone you have dialed is in the off-hook condition and/ therefore the central office will send you a-busy message.& This ends the questions for Unit 1.S Zn	  Wܱ
Ŀ߱!!	Ȼ						
Ȼ






4Ȼ.@Ȼٱ.@    3G__6@    


 

"
)
.@
/G___
:@
;.@  
1Gswitch 8@  .@
.Central	6OfficeS This Unit describes the equipment used to dial a telephone number and to route a call to its destination.S  
 	
(S  .@    3L_4G5O 6@    
 
,
/
3L_/
5O 
6G
:@
;.@  	1Lswitch7G 8@  S  
4
7	.@4	5@.@    4̺6@    
)
.@
/G
6G
:@
;S  
4
6
>/@/@    3G__6@    
/G___
:@
;/@  
1Gswitch 8@  S  
4

@S  
4S i	  W'(H $ooͿ8H H &oo78H H &oo	,LESSON4478H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2278H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 4, Unit 2.  After you have finished reading2 this material, press the space bar to continue.S ZLl	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S XMl Yn iciGl The basic function of thecentral office!-is to connect you with anothersubscriber in the network.
 '
Several different mechanisms, called
)switching systems,
<have been developedFover the last hundred years to control the way calls are connected. Switching systems;enable the central office to connect your telephone with/the telephone of the person you are calling.' Do you want to review more material?S i ZLl EAs telephone use increased, a number of inventors developed simpleIswitchboards which allowed a human operator to connect a caller to the$	person he or she wanted to reach.
 O
In 1891 Almon Strowger was issued a patent for an automatic switching systemwhich is now known as astep-by-step switch.2These switches becameenormously successful.' Do you want to review more material?S i ZLl Thestep-by-step switches1at the central office consist of huge banks ofJrotary switches with sets of wiper arm relays which move in response to4	each pulse produced by the rotary dial telephone. Therotary pulse telephone,has a rotary dial with ten equally spacedNfingerholes.  After the user rotates the dial, a spring rotates it back and*produces a series of electrical pulses. AEach pulse moves an electromagnet on a rotary switch one step.' Do you want to review more material?S i ZLl: Step-by-step switches suffer from a number of problems: .They are extremely slow by modern standards
 '
The physical equipment is very bulky DThey contain many moving parts which may be expensive to maintainE As a result, alternative switches have been developed, such as theCcrossbar	 switch
and thecrossreed switch.' Do you want to review more material?S i ZLl Electromechanical equipment, routes calls by means of hardware such asHswitches and wires connected to contacts. To change the way calls areG	routed, the hardware must be changed by rewiring circuits and so on. IThe next advance resulted from the use of computer controlled circuits	calledelectronic switching systems&'.  Since switching is controlled by:software rather than hardware, it is far more flexible.' Do you want to review more material?S i ZLl GModern telephone equipment is moving away from the rotary system andreplacing it with)electronically generated tone dialing.
 N
The new telephone equipment has 12 push buttons: ten for the digits 0 to 9,@and two marked * and # to provide access to special features. This system is called$dual tone multifrequency, or DTMF;, because instead ofMproducing pulses, pressing one of the buttons causes an electronic circuitCto generate two simultaneous tones to signal the central office.' Do you want to review more material?S i ZLl ?New services are available to businesses and residences withADTMF
Fwhich were4impractical or impossible with the old equipment.
 
Among these new features is
 third party calling
4in which up to three partiesIon different telephone lines can participate in a single conversation. Another feature iscall forwarding%&, which allows you to program your;phone to forward incoming calls to a different location.' Do you want to review more material?S n ZLl DTMF8has the following advantages over rotary dial phones: Decreased dialing time
 4
More compatible with current electronic circuitry ,Easier to maintain than the old equipment EAccess to features such as call forwarding and third party calling# This ends the review for Unit 2.S ZLl	  W True or False?R The basic task for the central office is to connect you with another subscriber0
 in the network by means of switching systems.S X X That's right, it'strue;.  Switching systems allow the central office to connect; your phone with the phone of the person you are calling.  Do you want another question?S Zn Zn No, it's	true.CThe main function of the central office is to connect your phoneM with the phone of the person you are calling by means of various switching systems.  Do you want another question?S Zn ZnJ A switch consisting of tiny relays encased in vacuum tubes is called a:  A Step-by-step	   B Crossbar   C Crossreed S X X XQ That's not it.  Step-by-step switches consist of huge banks of rotary switchesG with sets of wiper arm relays which move in response to dial pulses.
FCross-reed switches2	consist of tiny relays encased in vacuum tubes.  Do you want another question?S Zn Zn That's incorrect.Cross-reed switches+'consist of tiny relays encased in vacuumJ tubes.  They are more efficient than step-by-step or crossbar switches.  Do you want another question?S Zn Zn Correct.
Cross-reed switches2consist of tiny relays encased in vacuum tubes.I They are more efficient than either step-by-step or crossbar switches.  Do you want another question?S Zn ZnQ When a user dials a rotary telephone, switches at the central office receive a' series of electrical signals called:	 	 A 	Tones
   B 	Pulses
   C Multifrequencies S X X XS That is incorrect.  When you dial a push-button telephone you produce tones, but/ when you dial a rotary telephone you produce
-pulses.  Do you want another question?S Yn ZnJ That's right.  When you dial a rotary telephone you produce a series of
 electrical
pulses.>One pulse is sent for the digit 1, two for the digit 2, and* so on up to ten pulses for the digit 0.  Do you want another question?S Yn ZnS That's not it.  When you dial a push-button telephone you produce multifrequencyJ tones.  When you dial a rotary phone you produce a series of electrical
Hpulses.  Do you want another question?S Yn Zn True or False?! Switching calls by computer isless#$flexible than switching calls by
 electromechanical equipment.S X X No, it is	
false.!Switching calls by computer is1more6flexible than switchingQ calls by electromechanical equipment.  A computer can control the switching ofM calls by means of programs (software); to change the logic, you change the program.  Do you want another question?S Yn Zn You're right, it is	false.!Switching calls by computer is;more@flexible thanS switching calls by electromechanical equipment.  This flexibility stems from theP fact that computers control switching of calls by means of programs which are easily changed.  Do you want another question?S Yn Zn True or False? Step-by-step switches	cannot0work with DTMF tones unless they have special
 conversion equipment.S X X That's right, it'strue6. The tones must be converted into rotary pulses in9 order for the step-by-step switches to work with them.  Do you want another question?S Zn Zn Sorry, it'strue.@The DTMF tones must be converted into rotary pulses to enable/ the step-by-step switches to work with them.  Do you want another question?S Zn ZnP When several parties on different telephone lines can participate in a single conversation this is called:	 	 A 	Call forwarding
   B Call waiting
   C Third party calling S X X XR That's not right.  Call forwarding allows a person to forward incoming calls toO a different location.  When several parties on different telephone lines can7 talk to one another in a single conversation this is5third party calling.  Do you want another question?S Yn ZnQ No.  Call waiting allows a person to receive incoming calls even when the lineP is in use.  When several parties on different telephone lines can talk to one+ another in a single conversation this is)third party calling.  Do you want another question?S Yn Zn	 Right.Third party calling7allows several parties on different lines to talk toR one another in a single conversation.  The ability to have third party calls is" one of the advantages that DTMF$ has over the rotary pulse system.  Do you want another question?S Yn Zn True or False?P By 1985 virtually all local exchanges had replaced step-by-step switches with#
 more modern switching equipment.S   No, it is	
false.?Many local exchanges still rely on step-by-step switches forM directing calls.  DTMF telephones cannot be used in these exchanges if the5 central office does not have conversion equipment.& This ends the questions for Unit 2.S Zn	  W That's correct, it's	false.2Many local exchanges still rely on step-by-stepP switches for directing calls.  Some of these offices have installed equipmentP which converts DTMF tones into rotary pulses so that DTMF phones can be used.& This ends the questions for Unit 2.S Zn	  W;<p  >߱9:p    	t*.p
/        9p   <*p  p                        /0p  2 5p        =		p 	t*		p                        	/t*	0p         	9 	:p 	;t*	<p

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    O This Unit describes how the U.S. National Network links subscribers, and howE long-distance calls can be completed through many different paths.S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        *	0	;p*

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p            	#         	,	/p*	0	;p*

p  

p          *
"
-p          
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p            	#         	,	/p*	0	;p*

p  
	
p      

!p*
"
-p          
7 
8t  
:pp     p                            : p    p                 /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p   <*p  p                        /0p  2 5p        =		p 	t*		p                        	/t*	0p         	9 	:p 	;t*	<p

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*	0p         	9 	:p *

p  

p          
!t*
"p                     
7 
8t  
:p%p                                  : p                      /t *
1p       8

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*
	0p       	7	;p*

p  

p          
!t*
"p                     
7
8t  
:p"p                               78p  : p                      /t 0p*
18

p  
*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S  ;<p  >߱9:p    	t*.p
/        9p  ;<*p  p                        /0p  2 	5p      ;<p =		p 	t*		p                        	/t*
	0p       	7	;p*

p  

p          
!t*
"p                     
7
8t  
:p"p                               78p  : p           $0p*
18

p  
*


%p   
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    S i	  W'(H $ooͿ8H H &oo78H H &oo	,LESSON4478H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2378H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 4, Unit 3.  After you have finished reading2 this material, press the space bar to continue.S ZOl	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S XPl Zn iciGl KWhen the call you are placing goes beyond your local exchange area, yourMlocal central office makes a series of intervening connections to create aK	path from your telephone to the telephone of the person you are calling. JYour call is switched from one central office to another central office	over a
trunk line*, and the connection is then completed. MSwitching from one central office to another central office is very commonIfor most telephone calls, and a necessity for all long-distance calls.' Do you want to review more material?S i ZOl FAll telephone numbers in the United States are based on a series ofsystematic rules called the national numbering system.
 N
According to this plan, every main telephone in the U.S. is identified by aunique ten-digit number. ?Each ten-digit number consists of three parts: a three-digit
Aarea code,Lathree-digitlocal exchange, and a four-digit1subscriber number.' Do you want to review more material?S i ZOl    Area codesApermit direct dialing of any telephone in the U.S. without thehelp of an operator.
 M
Since all phones within an area code start with the same three digits, theOtotal number of different phone numbers within an area code is theoreticallylimited to 9,999,999. KAs the number of telephones and central offices continues to grow in theMU.S., the total number of area codes must be expanded to accommodate them.' Do you want to review more material?S i ZOl HTelephone services and rates are based on 193 geographic areas calledJLocal(Access and Transport Areas, or LATAs. ALATAGis a geographic area within which a local telephone company provides7	local services and access to long-distance services. KSome LATAs include an entire state; others are limited to a metropolitanarea. OEvery area code is assigned to only one LATA, but in some cases several area2codes are grouped together under a single LATA.' Do you want to review more material?S i ZOl 6The actual switching of each call is handled by the8U.S. National Telephone
NetworkAwhich is made up of thousands of central offices arranged in a
hierarchy.	 G	This network is divided into five classes of geographical areas, the#
largest of which is designated a
%Regional Center
5(Class 1 Office). #The next largest centers are the%Sectional Centers7(Class 2), followed in
size by the
Primary Centers
 (Class 3), the
/Toll Centers
<(Class 4), andfinally theEnd Offices,(Class five) - the local central offices.' Do you want to review more material?S n ZOl JIndividual subscribers are generally, but not exclusively, connected toClass 5 End Offices. MAll local calls are switched within the central office or through adjacent	Class 5 offices. HLong-distance switching is performed at Class 4, 3, 2, and 1 offices.
 H
The purpose of the network is to make connections by finding the mostKefficient path from the Class 5 office serving the caller to the Class 5office serving the party.# This ends the review for Unit 3.S ZOl	  WQ When you place a call which goes beyond your local exchange area, your call is- switched to another central office over a:	 	 A 
	Local loop
   B LATA
   C 
Trunk line S X X XR That's not it.  A local loop refers to the lines between a local subscriber andS a local central office.  When you call beyond your local exchange area, the call/ is switched to another central office over a-trunk line.  Do you want another question?S Yn ZnM That is incorrect.  A LATA is an area in which the local telephone companyS provides service.  When you call beyond your exchange area, the call is switched# to another central office over a!trunk line.  Do you want another question?S Yn ZnL That's right.  When you call beyond your local exchange area, the call is, switched to another central office over a*trunk line.7Switching is very common for most telephone calls.  Do you want another question?S Yn Zn True or False?R It is necessary to switch from one central office to another central office for
 all long-distance calls.S X X Right, it is
true.=When you place a long-distance call, your call is switchedN from one central office to another central office.  A series of interveningJ connections create a path from your phone to the party you are calling.  Do you want another question?S Zn Zn No, it is
true.=All long-distance calls require switching from one central$ office to another central office.  Do you want another question?S Zn Zn4 Local access and transport area (LATA) refers to:  A HA connection between two or more central offices within a single city	   B EAn area for which the local telephone company provides service and 
billing  C %The United States National Network S X X XQ That is incorrect.  Many calls involve connections between two or more central5 offices, but that is not the definition of a LATA.4A LATA is an area for which< the local telephone company provides service and billing.  Do you want another question?S Zn Zn Correct.D
The local telephone company provides service and billing within a LATA.ESome LATAs encompass an entire state while others are limited to a metropolitan area.  Do you want another question?S Zn ZnN No.  The U.S. National Network consists of the thousands of central offices2 which handle the actual switching of each call;"0a LATA is an area for which the8 local telephone company provides service and billing.  Do you want another question?S Zn ZnR The U.S. National Network is broken down into five classes of geographic areas,  the smallest of these is the:	 	 A 
	End Office
   B Primary Center
   C Regional Center S X X X Correct.  The
End Office5- the local central office - is the smallest.  The" Regional Center is the largest.  Do you want another question?S i Zn8 That's not it.  The Primary Center is larger than the
6End OfficeA- the local* central office - which is the smallest.  Do you want another question?S i Zn3 Sorry.  The Regional Center is the largest.  The
1End Office<- the local central office - is the smallest.  Do you want another question?S i ZnQ If there is heavy traffic on the most efficient phone route, can the telephone, company reroute the call to another path?S   That's right,yes>is the correct answer.  If there are technical difficultiesQ or heavy traffic in a particular area, a call can be rerouted.  The network ofI interconnected hierarchical exchanges allows this type of flexibility.  Do you want another question?S Yn Zn
 Sorry, butyesCis the correct answer.  The telephone company can reroute a callI if there is heavy traffic on the most efficient route.  The network ofH interconnected hierarchical exchanges allows for greater flexibility.  Do you want another question?S Yn Zn True or False?; Long-distance switching is performed at Class 5 offices.S   No, this is	false.?Long-distance switching is performed at Class 4, 3, 2, and 1N offices, but it is not performed at Class 5 End Offices - the local central
 office.& This ends the questions for Unit 3.S Zn	  W Correct, it is	false.:Long-distance switching is not performed at Class 5 End@ Offices, but it is performed at Class 4, 3, 2, and 1 offices.& This ends the questions for Unit 3.S Zn	  W``	 O      &@   )O         2
@ O   #@   &O            23	
``		@   	#O               	2

@
 O  Central Office  
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@R This Unit describes how telephone traffic engineers design telephone systems toM meet demand during the busiest periods, so that calls will not be blocked.S  `` Lͻ   2
@ O   #@   &O        .L23	
``		@   	#O               	2

@
 O  Central Office  
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@S  `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ O    $@ %O   (@  *O        2
@ O     %@   
(O          23

``

@
 O   
#@  
%O 
&@ 
'O           
2@@S  `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ Lͻ%O   (@  *O        2
@ O    $L23

``

@
 O   
#@  
%O 
&@ 
'O   
*L 

+O       
2@@S  `` Lͻ   2
@ O   #@   &O        .L23	
``		@	 Lͻ	1O 	2

@
 O  Central Office
0L
2
3``@ Lͻ%O   (@  *O        2
@ O    $L23

``

@
 L

"BLOCKED
)O 
*L 

+O       
2@@S i	  W'(H $ooͿ8H H &oo78H H &oo	,LESSON4478H 		H 		&oo	7	8H 

H 

&oo
7
8H H &oo,UNIT2478H H &oo78H 

H 

&oo
7
8H H $____________oo______________8H H'(H5&R Please open your workbook to Lesson 4, Unit 4.  After you have finished reading2 this material, press the space bar to continue.S ZRl	   Would you like to:  A %Review key concepts from this Unit	   B #Answer questions about this Unit   C Go on to another Unit S XSl Zn iciGl Thenetwork busy signal7indicates that although the telephone you are tryingJto reach may be free, there are no free circuits available to reach the

number.
 
Blocking?

refers to an inability to connect two telephones because all2possible paths between them are already in use.' Do you want to review more material?S i ZRl  Telephone traffic engineering0"is the science of designing telephone systemsMfor maximum efficiency by measuring and predicting the number of telephone*calls expected for a particular system.
 N
Telephone specialists called traffic engineers usually focus on patterns oftelephone use during the
busy hour,)(the hour of the day when phone traffic0is highest for a particular telephone system. KTraffic may be monitored by having human operators simply count calls by-hand, or by using computers to do the job.' Do you want to review more material?S i ZRl CCSDis a common measure of telephone traffic.  Specifically it is theOaverage number of calls in progress for the full duration of a period of 100	seconds. +Another common measure of traffic is the	-erlang 3, which is the average numberFof calls in progress for the full duration of a period of one hour. .Both erlangs and CCS can be computed from a0peg count:of the total number ofHtelephone calls during a given period, and the average call duration.' Do you want to review more material?S n ZRl Thegrade of service6indicates the probability that a given call will be$blocked by a network busy signal.
 K
A grade of service of P01 means that 1 call per 100 will not get throughduring the busy hour. Thetrunkage factor:is the number of outside lines divided by the number ofGtelephone stations.  Thus, a user with 25 outside lines to serve 100+telephones has a trunkage factor of 1:4.# This ends the review for Unit 4.S ZRl	  W1 "Telephone traffic engineering" refers to the:  A &Science of coaxial cable placement.	   B ,Designing of efficient telephone systems.   C (Correct placement of central offices. S X X X< That's not correct.  Telephone traffic engineering is the:designing of efficient telephone systems<by measuring and predicting the number of telephone calls$ expected for a particular system.  Do you want another question?S Zn Zn8 That's correct.  Telephone traffic engineering is the6designing of efficient telephone systems<by measuring and predicting the number of telephone calls$ expected for a particular system.  Do you want another question?S Zn Zn< That's not correct.  Telephone traffic engineering is the:designing of efficient telephone systems<by measuring and predicting the number of telephone calls$ expected for a particular system.  Do you want another question?S Zn ZnR An erlang is the average number of calls in progress for the full duration of a
 period of:	 	 A 	One hundred seconds
   B 
One minute
   C One hour S X X XK That's incorrect.  CCS refers to the average number of calls per hundred seconds.;
An erlang is the average number of calls in progress perChourG.  Do you want another question?S Zn ZnC Sorry.  An erlang is the average number of calls in progress perAhour.  Do you want another question?S Zn Zn That's right.;An erlang is the average number of calls in progress perHhourL.  Do you want another question?S Zn ZnQ How many calls will be blocked during the busy hour if the grade of service is P01?	 	 A 	1 call out of 10
   B 1 call out of 100
   C 1 call out of 1000 S X X X: That's incorrect.  A grade of service of P01 means that81 call out of 100	Jduring& the busy hour will not get through.  Do you want another question?S Zn Zn8 That's correct.  A grade of service of P01 means that61 call out of 100	Hduring& the busy hour will not get through.  Do you want another question?S Zn Zn: That's incorrect.  A grade of service of P01 means that81 call out of 100	Jduring& the busy hour will not get through.  Do you want another question?S Zn Zn Business users consider atrunkage factor%*of 1:4 to be necessary for average7 office needs.  The trunkage factor is the number of:	 	 A 5	Telephones divided by the number of outside lines.
   B 9Outside lines divided by the number of intercom lines.
   C 5Outside lines divided by the number of telephones. S    ) That's incorrect.  The trunkage factor'is the number of8outside lines divided by/ the number of individual telephone stations.& This ends the questions for Unit 4.S Zn	  W) That's incorrect.  The trunkage factor'is the number of8outside lines divided by/ the number of individual telephone stations.& This ends the questions for Unit 4.S Zn	  W' That's correct.  The trunkage factor%is the number of6outside lines divided by/ the number of individual telephone stations.& This ends the questions for Unit 4.S Zn	  W	#	%	'	)	+
#
%
'
)
+!
#p       *x+p-!"*x+p-
!
"p        
*x
+_______________"#p     (x+p,-_______________*@<.S Now you can try applying the material from Lesson 4.  In this exercise, you willP make a series of calls to track down your Uncle Sid's new telephone number soP that you can call him for his 65th birthday.  To complete each call, you will? need to answer several questions about the telephone system.S [n	  WO To successfully complete this exercise you will need to be familiar with the( basic concepts explained in Lesson 4. Would you like to:  A Go on to the exercise   B "Review the material in Lesson 4 S Vl iciGlP Your Uncle Sid recently retired after working for 48 years for the New JerseyM Life Insurance Company.  He and his wife Lucille have just moved to GoldenO	 Age Village which is located just outside of Phoenix, Arizona.  Today is hisN 65th birthday, and you'd like to give him a call.  Unfortunately, their newN
 phone number is unlisted, so you need to get it from one of your relatives.S Tm	  W#+
		)
	A
  
'
?  Ȼ'CDHJɼ'CDH

Byou'@your brotherO Let's say that you and your brother both live in the same part of town.  YouQ decide to try calling him first since he is usually on top of family business.S ZUl	  N When you pick up the handset (the receiver) to call your brother, the first' thing the central office does is to:	 	 A *	Send a ring-back tone to your telephone
   B )Transmit a dial tone to your telephone
   C 2Register an off-hook message for your telephone S   	P No, that's not it.  The ring-back tone would not be sent until after you have< dialed a number.  Before that happens, the central office:registers an off-hook message for your telephone.S 
Tl	  W= Almost.  But before a dial tone is sent the central office;registers an off-hook message for your telephone.S 
Tl	  WJ That's right.  The central office detects a request for service when it4 registers an off-hook message for your telephone.S 
Tl	  W* a * a# aaaaaaaa* aa	 	 aaaaaaaaa	$@ 	) a	*@ 
	A
 aa
 
 aaa
off-hook
 @             
-
.@ 
?   aȻ
 @ Framingham    CDHJɼ @ Central OfficeCDH

 @               
Byou$@ ' a*@ @your brotherL Now your local central office "knows" that you would like to make a call.S ZUl	  WH How did your local central office detect your request to make a call?  A A flow of loop current	   B Dial pulses   C Dual tone multifrequency S  
 / That's right.  When the handset is lifted, a-flow of loop currentBindicates to- the CO that you would like to make a call.S Tl	  WR No.  With a rotary telephone, dial pulses signal the CO and indicate the numberL you wish to call.  But even before dialing, when the phone is off-hook, aJflow of loop current0indicates that you would like to make a call.S Tl	  WP That's incorrect.  With a push-button phone, dual tone multifrequency signals9 the number you have dialed to the CO.  Before dialing,7a flow of loop currentQ indicates to the CO that you wish to place a call.  This occurs when the phone  is in the off-hook condition.S Tl	  W 
# aaaaaaa+ a	 	 aaaaaaaaa	$@ 	) a	*@ 
	A
 aa
 
 aaa
dial
 a
tone
 @             
-
.@ 
?   aȻ
 @ Framingham    CDHJɼ @ Central OfficeCDH

 @               
Byou$@ ' a*@ @your brotherR You now have a dial tone.  The next step is to tell the central office whom you would like to call.S ZUl	  WL You and your brother live in the same neighborhood.  Your phone number isM 555-6796, while his is 555-0135.  How many central offices are involved in( connecting your call to your brother?	 	 A 	None
   B One
   C Two S   N That's incorrect.  Every call must be switched through at least one centralJ office.  In this case, because you and your brother have the same local exchange, onlyone1central office is needed to complete the call.S Tl	  WN That's correct.  All numbers within the same local exchange are assigned toLone central office.S Tl	  WO Sorry.  All numbers within a local exchange are assigned to the same central: office.  Therefore, your call would be switched at this8one<central office.S Tl	  W 
# aaaaaaa+ a	 	 aaaaaaaaa	$@ 	) a	*@ 
	A
 aa
 
 aaa
 aaaaaaaaa
 @             
-
.@ 
?   aȻ
555 @ Framingham    CDHJɼ @ Central OfficeCDH

 @               
Byou$@ ' a*@ @your brotherP Good.  You have now signalled the number that you wish to dial to the centralQ office.  The next step is for the central office to connect your telephone and your brother's telephone.S ZUl	  WR In your local central office there are large banks of rotary switches with setsS of wiper arm relays which move in response to each pulse produced by your rotaryN dial telephone.  Which switching system is being used to connect your call?	 	 A 	Step-by-step
   B Crossbar
   C Crossreed S   > That's correct.  This is the definition of the Strowger, or<step-by-step
Iswitch.Q Although modern alternatives exist, the step-by-step switch is still in use in many areas.S Tl	  W@ That's incorrect.  This is the definition of the Strowger, or>step-by-stepQ switch.  The crossbar switch was smaller, faster, and cheaper to maintain than the step-by-step.S Tl	  W2 No.  This is the definition of the Strowger, or0step-by-step=switch.  TheE cross-reed switch consists of tiny relays encased in vacuum tubes.S Tl	  W	 ) 
# aaaaaaa+ a?\\  `H'K//	 	 aaaaaaaaa	ring-back	$@ 	) a	*@ 
	A
 aa
 
 aaa
tone	
 aaaaaa
 @             
-
.@ 

6ringing
?   aȻ
 @ Framingham    /CDHJɼ @ Central OfficeCDH

 @               
Byou$@ ' a*@ @your brotherO While we wait for your brother to answer, you can see that this was a fairlyN simple connection to complete.  It involved local loops to a single central office, your local exchange.S n	  W a	 a a
 aJM                                                                      O                                                                        ? aaC aH aK aL	 	 aaaaaaaaa	 aaaaaaaa	$@ 	*@ 
	@ aaaaaaaaaa	J 
 aa
 
 aaa
 a
voice
 L               
6 a
7voice
< aa
? aaa
C 
L a aȻ
 L !@Framingham ,L   /CDHJɼ L !@Central OfficeCDH

 L               
Byou$@ *@ @your brotherQ Your brother tells you a hot rumor about Aunt Lucille, who didn't want to moveS to Phoenix because she loves gambling and says that there are no good racetracksP nearby.  Apparently she went to Roosevelt Raceway the night before they moved and lost $3500.S YUl	  WM Unfortunately, however, he doesn't have Uncle Sid's new number.  But he is' pretty sure that your sister has it.	 True or False?S When you hang up the handset after talking with your brother, the on-hook signal. tells the central office to seize the line.S   No, it's		false.AThe line is seized when the connection is made.  When you hangF up the handset the on-hook signal tells the CO to release the line.S Tl	  W You're right, it is	false.2When the handset is returned to the cradle, theL on-hook signal tells the CO to release the line.  A line is seized when a connection is made.S Tl	  W
  aaaaaaa	H aaaaaa
  aaaaaaa
I aaaaaaa  aaaa
I aaaaaaa	  aaaaaa	H aaaaaa	  aaaa
		$ a	* aa
	A	K aaaaa
  a
 a
  
  aaaaaaaaaaaaaaaaa
?  
M aaaȻ9
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaCDHJɼ  aaaaaaaaaaaaaaaaaaaaCDH

  aaaaaaaaaaaaaaaaa
Byou$ a* a@ aAyour sister* aR The line has been released, so now you can go ahead and try calling your sister- to see if she has your uncle's new number.S n	  W#+
		)
	A
  
'
?  Ȼ'CDHJɼ'CDH

Byou'@ aAyour sisterO You will again have to answer several questions about this connection before* successfully completing the phone call.S  Z Ul	  WQ You only have one telephone in your small apartment, the same rotary phone youP had when you moved in ten years ago.  When you place the call to your sister,L using her phone number, how will this be signalled to the central office?	 	 A 	Dial pulses
   B 
Dual tones
   C DTMF S ! " #7 Correct.  Numbers dialed on rotary telephones create
5dial pulse@signals.  If youR had a push-button phone, it would signal the number you wanted to call with two# simultaneous tones, called DTMF.S $Tl	  WS That's incorrect.  If you had a push-button telephone, pushing the buttons wouldM cause the phone to send two simultaneous tones, called DTMF, to signal the9 central office.  You have a rotary phone which creates7dial pulsesCto signal the central office.S $Tl	  WP That's not it.  DTMF refers to dual tone multifrequency; choices B and C bothR refer to the way that push-button telephones signal the central office.  With a! rotary telephone, a pattern ofdial pulses+signals the central office.S $Tl	  W* a * a# aaaaaaaa* aaa	 	 aaaaaaaaa	@ 	  a	!@ 	) aaa
	A
 aa
 
 aaa
?
 aaaa
@             
$
%@ 
' aa
?   aȻ

@ Framingham    	& aaaaaaCDHJɼ@ Central Office' aCDH

@               
' a
Byou@  a!@ ' aAyour sisterP Your sister, Penelope, is studying for a Ph.D. in Medieval Studies at HarvardR and lives about 30 miles away in Cambridge, MA.  Her number is 999-8233.  Yours is still 555-6796.S %Y%Ul	  W True or False?Q When you call your sister, the call will probably be switched through at least
 two central offices.S & 'R That's right, it is true.  Since your sister lives 30 miles away, and her phoneR number begins with 999 while yours begins with 555, it is unlikely that you areP both connected to the same central office.  Therefore, the call will probably4 have to pass through two or more central offices.S (Tl	  W No, it is
true.>Since your sister lives 30 miles away, and her phone numberQ begins with 999 while yours is 555, it is unlikely that you are both connectedP to the same central office.  Therefore, it will probably have to pass through two or more central offices.S (Tl	  W* a * a# aaaaaaaa* aaa	 	 aaaaaaaa	@ 	  a	!@ 	( a	-@ 	3@ 
	A
 aa
 

 aaaaaaaaa
@             
$
%@ 
' a
)L            
5@   
?   aȻ

@ Framingham    &
)@ Cambridge3L  5@   CDHJɼ@ Central Office' a)@ Central OfficeCDH

@               
' a
)L            
5@   
Byou@  a!@ ' a-@ 3@ Ayour sisterO Before the call to your sister can be completed, you will need to answer one more question.S )Y)Ul	  W True or False?5 To complete the call to your sister the connection3must8be made through a Class
 4 Office.S * + No, it's		false.:Two Class 5 End Offices are involved in this call - theS Framingham central office and the Cambridge central office.  A Class 4 Office is. a toll office, and this is not a toll call.S ,Tl	  W That's right, it's	false.5Two Class 5 End Offices are involved in this call.Q If the call to your sister was a toll call, a Class 4, 3, 2, or 1 Office would/ also be required to complete the connection.S ,Tl	  W* aJ * aJ # aaaaaaaaL* aaaL	 	 aaaaaaaa	@ 	  a	!@ 	( a	-@ 	3@ 	A aaaaaaaaa	J 
 aa
 
 aaaaaaaa
@             
$
%@ 
' a
)L            
5@   
? aaa	
C
I a
J aȻ

@ Framingham    &
)@ Cambridge3L  5@   CDHJɼ@ Central Office' a)@ Central Office9off-hookCDH

@               
' a
)L            
5@   

8
Byou@  a!@ ' a-@ 3@ Ayour sisterQ Your sister's telephone is sending an off-hook signal to the Cambridge central
 office.S -Z-Ul	  WP If your sister's telephone sends an off-hook signal to the local CO, you will
 hear a:	 	 A 	Ring-back tone
   B Dial tone
   C Busy signal S . / 0O That's not it.  If you were hearing a ring-back tone, her telephone would beQ ringing.  Since her telephone is sending an off-hook message to the CO, she is= already using her phone, and you would hear a busy signal.S 1[1n	  WS That's incorrect.  You have already dialed her telephone number, so you would noR longer be hearing a dial tone.  Her telephone is sending an off-hook message toM the CO, and that means that she is already on the telephone.  You would be hearing a
busy signal.S 1[1n	  WP You've got it.  Your sister's telephone is sending an off-hook message to theS Cambridge central office because she is already using the telephone and her line+ has been seized.  You would be hearing a)busy signal.S 1[1n	  W Do you want to:  A 5Hang up and try calling your sister's number again	   B GTry calling your mother in California to get your uncle's new number S 2Tl 3Tl* aJ * aJ # aaaaaaaaL* aaaL	 	 aaaaaaaa	@ 	  a	!@ 	( a	-@ 	3@ 	A aaaaaaaaa	J 
 aa
 
 aaaaaaaa
@             
$
%@ 
' a
)L            
5@   
? aaa	
C
I a
J aȻ

@ Framingham    &
)@ Cambridge3L  5@   CDHJɼ@ Central Office' a)@ Central Office9off-hookCDH

@               
' a
)L            
5@   

8
Byou@  a!@ ' a-@ 3@ Ayour sisterG It is still busy.  Maybe you should try calling your mother instead.S 1[1Ul	  W( a ( a ! aaaaaaaaaaaaaa ' aaa. a	 	 aaaaaaaaa	# a	, aaa
	B
  aa
 
 aaaa
* aa
@   aȻ
 aaaa* aaaaaDEIKɼ
* aDEI

% a
Cyou a% a* aByour motherQ Your mother lives in San Francisco.  She usually doesn't go out in the evening= during the week, so you decide to try calling her at home.S 4Z4Ul	  WN As you call your mother in San Francisco your call is first connected to a:  A Class 2 Sectional Office	   B Class 4 Toll Office   C Class 5 End Office S 5 6 7N No.  The call may pass through a Class 2 Sectional Center as it is switched< through the long-distance network, but it first goes to a:Class 5 End Office, your local central office.S 8Tl	  WN That's not it.  Although your call will pass through a toll office as it is> switched into the long-distance network, it first goes to a<Class 5 End Office which is your local central office.S 8Tl	  W; That's correct.  The call to your mother first goes to a9Class 5 End Office,MtheK local central office.  It is then routed into the long-distance network.S 8Tl	  W;<p  >C߱9:p    C'`		t*.p
/        9p  ;<*
? you	'`p  p                        /0p  2 	5p      ;<p =		your			p 	*	Ŀ	"p 	#         	,	/p*	0	;p*	
mother

p  
	
p      
    
!p*
"
-p          
7 
8t  
:pp      p                            : p     p                 /t *
1p       8

p  
t*

p          
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    Q Your call to your mother in San Francisco might pass through a number of these9 offices as it moves through the long-distance network.S 9X9Ul	  WQ If you called your mother again at the same time tomorrow, would the call pass6 through the same offices and follow the same route?S : ;M No, that's not necessarily true.  The particular connections depend on theS pattern and number of calls arriving at and leaving each office.  The network ofR hierarchical exchanges provides alternate routes when phone traffic gets heavy.S <Tl	  W That's right, the answer isno.+!There are many possible routes the phoneN company can use to complete a call.  It there are technical difficulties orS if traffic is heavy in a particular geographical area, calls are often rerouted.S <Tl	  W;<p  >C߱9:p    C'`		t*.p
/        9p  ;<*
? you	'`p  p                        /0p  2 	5p      ;<p =		your			p 	*	            	"p 	#         	,   	/t*	0       	;p*	
mother

p 

	
p      
    
!t*
"           
-p          
7
8t  
:pĿp                         78p  : p    
p       %0p*
18

p  *

&p  
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    Q For example, if you called your mother tomorrow night, the path of connections- might change and look something like this.S =n	  W;<p  >C߱9:p    C'`		t*.p
/        9p  ;<*
? you	'`p  p                        /0p  2 	5p      ;<p =		your			p 	*	            	"p 	#         	,   	/t*	0       	;p*	
mother

p 

	
p      
    
!t*
"           
-p          
7
8t  
:pĿp                         78p  : p    
p       %0p*
18

p  *

&p  
(
)p            
p      &            6p 7t*8p  !p  78p  "#p$                    M The trunks weren't busy, and your call has been connected through the long distance network.S >Z>Ul	  WN When your mother answers the phone, she tells you that she's not in her ownQ house!  She took the call at your Aunt Mabel's house by using a new feature on her phone system called:	 	 A 	Third party calling
   B Call forwarding
   C Call waiting S ? @ AQ That's not it.  In third party calling, up to 3 parties on different telephoneC lines can participate in a single conversation.  Your mother hasAcall forwarding,Fa feature which allows her to forward incoming calls to a different location.S BXBn	  W2 That's right.  Your mother has a feature called0call forwarding@which allowedS her to program her telephone to forward any incoming calls to your aunt's house.S BXBn	  WP That's incorrect.  Call waiting is a feature which would allow her to receive4 incoming calls while she was using the telephone.3Call forwardingCallowed herP to program her telephone to send any incoming calls to another phone, such as your aunt's.S BXBn	  WO You happen to know that the Nob Hill central office serving your mother usesR step-by-step switches to connect calls.  If your mother has a touch-tone phone,B	 can she still use it to make calls through this central office?S C D That's right, the answer isyes..!As long as the local central office has the& equipment to convert the DTMF tones+$into the rotary pulses necessary for theD step-by-step switches, your mother can use her push-button phone.S ETl	  W Sorry, the correct answer isyes.."As long as the local central office has the& equipment to convert the DTMF tones+$into the rotary pulses necessary for theD step-by-step switches, your mother can use her push-button phone.S ETl	  W;<p  >C߱9:p    C'`		t*.p
/        9p  ;<*
? you	'`p  p                        /0p  2 	5p      ;<p =		your			p 	*	            	"p 	#         	,   	/t*	0       	;p*	
mother

p 

	
p      
    
!t*
"           
-p          
7
8t  
:p
Ŀp                         78p  : 
p    
p       %0p*
18
	

p  *

&p  
(
)p            	'`
p      &            6p 7t*8p Aunt !p  78p  
Mabel"#p$                    R Unfortunately, your mother didn't bring her address book with her when she cameR to play bridge.  Aunt Mabel doesn't have the number because she and Sid haven't spoken since 1953.S Fn	  W	#	%	'	)	+
#
%
'
)
+!
#p       *x+p-!"*x+p-
!
"p        
*x
+_______________"#p     (x+p,-_______________*@<.2 Your mother says, "Why didn't you send a card?"Q Even though you will not be able to call Sid on his birthday, you did identifyI all the steps needed to complete these calls.  Congratulations on your* successful completion of this exercise.S iciGl	  W  O  ͻ  J 	LESSON 4  O   ͼ   O       	Main MenuS H  J 	LESSON 4   )	Unit 1 - The Steps of a Telephone CallS I  O  ͻ  J 	LESSON 4  O   ͼ   O       	Unit 1 - The Steps of a Telephone CallS J  G  J 	LESSON 4  G p()G  @	G  	Unit 1 - The Steps of a Telephone CallS K  J 	LESSON 4   	Unit 2 -Dialing & SwitchingS L  O  ͻ  J 	LESSON 4  O   ͼ   O       	Unit 2 -Dialing & SwitchingS M  @ O @ĿJ 	LESSON 4  O/@_O @	Unit 2 - Dialing & SwitchingS N  J 	LESSON 4   	Unit 3 -The U.S. National NetworkS O  O  ͻ  J 	LESSON 4  O   ͼ   O       	Unit 3 -The U.S. National NetworkS P  *** OJ 	LESSON 4  O @%	Unit 3 - The U.S. National NetworkS Q  J 	LESSON 4   	Unit 4 -Traffic and Grade of ServiceS R  O  ͻ  J 	LESSON 4  O   ͼ   O       	Unit 4 -Traffic and Grade of ServiceS S  O @ O @ OJ 	LESSON 4  O@O?@ O  O@O@O(	Unit 4 - Traffic and Grade of ServiceS T  J 	LESSON 4   	Unit 5 -The Birthday CallS U  O  ͻ  J 	LESSON 4  O   ͼ   O       	Unit 5 - The Birthday CallS V	 J 	LESSON 4 	
 	Unit 5 - The Birthday CallS WF @CG D@PressIG J@spaceOG S XD @AG 	B@SelectHG I@YJG K@orMG N@NOG S YD @AG 	B@SelectHG I@TJG K@orMG N@FOG S ZG @DG 	E@SelectKG L@A-COG S [D @AG 	B@SelectHG I@AJG K@orMG N@BOG S \G @DG 	E@SelectKG L@1-3OG S ]G @DG 	E@SelectKG L@1-4OG S ^N @ SelectKG L@1-5OG S _N @ SelectKG L@1-6 S `N @ SelectKG L@1-7 S aN @ SelectKG L@1-8 S bN @ SelectKG L@1-9 S cN @ SelectKG L@A-GOG S dN @ SelectKG L@A-D S eN @ SelectKG L@A-E S fN @ SelectKG L@A-F S gN @ SelectKG L@A-H S hS iS jS kS lS mS nS oS   