Canon FACSIMILE BASIC 2000, BASIC 2000 Service Manual

APR.2000

HY8-53A2-00Z

COPYRIGHT © 2000 CANON INC. FACSIMILE BASIC2000 APR.2000 PRINTED IN JAPAN (IMPRIME AU JAPON)

FACSIMILE

FACSIMILE

BASIC

2000

REVISION 0

Application

This manual has been issued by Canon Inc. to provide information necessary to self-study to tech­nicians who service facsimile products. This manual covers all localities where the facsimile
products are sold. For this reason, there may be information in this manual that does not apply to
your locality.

The following paragraph does not apply to any countries where such provisions are incon­sistent with local law.

Trademarks

The product names and company names described in this manual are the registered trademarks of
the individual companies.

Copyright

This manual is copyrighted with all rights reserved. Under the copyright laws, this manual may
not be copied, reproduced or translated into another language, in whole or in part, without the
written consent of Canon Inc.

Copyright © 2000 by Canon Inc.
CANON INC.
Office Imaging Products Technical Support Dept. 3
5-1 Hakusan 7-Chome, Toride-city, Ibaraki 302-8501, Japan

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PREFACE

This manual describes the general technology and principles of CANON facsimile operation so
that those studying facsimiles for the first time and those already servicing facsimiles can gain a
further understanding of these equipment.

Chapters 1 and 2 describe an overview of telephony and facsimile operation. Chapter 3 onwards
describes the reading section, recording section, communications and electrics in more detail.
Those studying facsimiles for the first time should begin their studies with Chapters 1 and 2.
Those already servicing facsimiles or those who already understand facsimiles to a certain extent
may refer to chapters that meet their particular requirements.
This manual is made up of the following chapters:

Chapter 1: BASIC OF TELEPHONE
Chapter 2: GENERAL DESCRIPTION OF A FACSIMILE
Chapter 3: READING SECTION
Chapter 4: RECORDING SECTION
Chapter 5: G3 FACSIMILE COMMUNICATIONS
Chapter 6: FACSIMILE SYSTEM
APPENDIX

The appendix is followed by a glossary with supplementary explanations of technolog y that could
not be described in the main text. Refer to this glossary as necessary.

Words colored red in this document are explained in the “GLOSSARY” in the “APPENDIX” of
this document.

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CONTENTS

PREFACE.........................................................................................i

CONTENTS.....................................................................................ii

CHAPTER 1 BASIC OF TELEPHONE

INTRODUCTION TO THE TELEPHONE.....................................1-2

Parts of the Telephone..............................................................1-2

Making a Call............................................................................1-3

How do you make a call?..........................................................1-4

Voice Frequencies Carried by the Telephone...........................1-4

STRUCTURE OF A TELEPHONE...............................................1-5

Transmitter (Microphone)..........................................................1-6

Receiver (Speaker)...................................................................1-7

Voice Circuit..............................................................................1-7

Hook Button..............................................................................1-8

Dial............................................................................................1-9

Bell (Speaker).........................................................................1-10

TYPES OF TELEPHONES.........................................................1-11

Dial Telephones......................................................................1-11

Pushbutton Telephones..........................................................1-11

Digital Telephones..................................................................1-12

CIRCUIT DIAGRAM IN THE TELEPHONE................................1-13

Dial Telephones......................................................................1-13

Pushbutton Telephone............................................................1-14

INTRODUCTION TO THE TELEPHONE NETWORK................1-15

Parts of a Telephone Network ................................................1-15

Basic Structure of a Telephone Network System ...................1-19

Nationwide Telephone Network (In case of Japan)................1-20

TELEPHONE EXCHANGES......................................................1-25

Types of Exchanges ...............................................................1-25

The Exchange.........................................................................1-26

CHAPTER 2 GENERAL DESCRIPTION OF A FACSIMILE

WHAT IS A “FACSIMILE?”...........................................................2-2

Established Rules of Communication.......................................2-2

Control Procedure.....................................................................2-2

Facsimile Groups......................................................................2-3

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Telephone Lines.......................................................................2-3

Types of ITU-T Recommendations...........................................2-4

How Images are Transmitted ...................................................2-8

STRUCTURE OF A FACSIMILE................................................2-13

Reading Section .....................................................................2-15

Recording Section ..................................................................2-18

MODEM..................................................................................2-21

NCU board (Network Control Unit board)...............................2-22

System Control Section..........................................................2-22

THE FUTURE OF FACSIMILES................................................2-23

Color Facsimiles.....................................................................2-23

LAN-networked Facsimiles.....................................................2-23

Internet Facsimiles .................................................................2-24

CHAPTER 3 READING SECTION

INTRODUCTION..........................................................................3-2

READING METHODS..................................................................3-3

Sheet Reading Method.............................................................3-3

Book Reading Method..............................................................3-4

ADF Type .................................................................................3-4

CONTACT SENSOR..................................................................3-10

Structure of Contact Sensor ...................................................3-10

Features of Contact Sensor....................................................3-10

IMAGE DATA PROCESSOR.....................................................3-14

Various Image Data Processing............................................3-14

CHAPTER 4 RECORDING SECTION

INTRODUCTION..........................................................................4-2

IMAGE DATA PROCESSING SECTION.....................................4-3

Image Area Separation Processing, Smoothing Processing

and Selector .............................................................................4-4

Reproduction Ratio Processing Section...................................4-8

Ink Saving/Toner Saving ........................................................4-11

PAPER FEED SECTION ...........................................................4-12

Pickup Section........................................................................4-12

Feed/Eject Section .................................................................4-17

Detection of Recording Paper Jams.......................................4-19

PRINTING SECTION.................................................................4-24

LBP (LASER Beam Printer)....................................................4-24

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Printing by LASER..................................................................4-24

Flow of Printing.......................................................................4-26

Video Control Section/Printer Engine Control Section............4-27

LASER/Scanner Section.........................................................4-32

Printing Process......................................................................4-34

Toner Cartridge.......................................................................4-46

BJ (Bubble Jet) Printer............................................................4-48

Printing by Bubbles.................................................................4-48

Printing Section.......................................................................4-50

Carriage Section.....................................................................4-51

Purge Unit...............................................................................4-56

BJ Cartridge............................................................................4-58

CHAPTER 5 G3 FACSIMILE COMMUNICATIONS

INTRODUCTION..........................................................................5-2

WHAT IS A “G3 FACSIMILE?”.....................................................5-2

G3 FACSIMILE IMAGE TRANSMISSION....................................5-3

Structure of Image Signals........................................................5-3

Transmission Time....................................................................5-5

CODING SCHEMES ....................................................................5-8

Why is Coding Necessary?.......................................................5-8

MH Coding Scheme (One-dimensional Coding Scheme).......5-10

MR Coding Scheme (Two-dimensional Coding Scheme).......5-17

MMR Coding Scheme.............................................................5-28

JBIG Image Compression Encoding Scheme.........................5-29

MODULATION METHOD...........................................................5-45

Modulation and Demodulation................................................5-45

Shift and Modulation Methods ................................................5-46

Modulation Methods up to 9600 bps.......................................5-47

High-speed MODEMs above 14400 bps ................................5-55

V.17 (V.33) MODEM Technology ...........................................5-55

V.34 MODEM Technology......................................................5-73

TRANSMISSION CONTROL PROCEDURES...........................5-89

Outline of Transmission Control Procedures..........................5-89

Signal Types...........................................................................5-90

Basic Transmission Control Procedure...................................5-91

Procedures for Performing Individual Page Control

(Q signals).............................................................................5-100

Training.................................................................................5-102

Method for Detecting Image Signal Transmission Errors .....5-104

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Option Signals ......................................................................5-106

Structure of Binary Signals...................................................5-107

Example of G3 Procedures ..................................................5-122

ECM Communications..........................................................5-123

CHAPTER 6 FACSIMILE SYSTEM

INTRODUCTION..........................................................................6-2

SCNT BOARD..............................................................................6-3

System Control Section............................................................6-3

Communications Control Section .............................................6-4

Reading Control Section...........................................................6-4

Printer Control Section .............................................................6-4

NCU BOARD................................................................................6-5

Off-hook Detection....................................................................6-6

Formation of DC Loop ..............................................................6-6

Detection of Calling Identification (CI) ......................................6-9

Line Signal Monitor.................................................................6-10

Dial Control.............................................................................6-11

2-wire/4-wire Conversion........................................................6-12

Protective Circuits...................................................................6-12

Telephone Connection Control...............................................6-14

Relay Operations....................................................................6-17

OPCNT BOARD.........................................................................6-18

Detection of Button Input........................................................6-18

LED Lighting Control ..............................................................6-21

Display Indication Control.......................................................6-21

FLOW OF IMAGE SIGNALS......................................................6-22

Transmission ..........................................................................6-22

Reception ...............................................................................6-23

POWER SUPPLY UNIT.............................................................6-24

Switching Regulator................................................................6-24

Configuration of Power Supply Unit on a Facsimile ...............6-31

G4CNT BOARD .........................................................................6-32

APPENDIX

TRANSMISSION LINES OF TELEPHONE LINES ..................... A-2

CHARACTERISTICS OF TELEPHONE LINE (ANALOG).......... A-4

Telephone Line Band .............................................................. A-4

Characteristics of Telephone Network Components ............... A-5

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Factors of Telephone Line Deterioration..................................A-6

FACSIMILE COMMUNICATION NETWORK SERVICES &

MINIFAX (JAPAN ONLY).......................................................... A-10

F-NET ....................................................................................A-12

Minifax I (MF-I).......................................................................A-16

Minifax II (MF-II).....................................................................A-17

TELEPHONE LINE BAND & SIGNAL SPECTRUM..................A-19

S/N.............................................................................................A-20

POLARITY INVERSION ON EXCHANGE ................................A-21

FACTORS WHICH CAUSE DETERIORATION

IN QUALITY OF FACSIMILE TRANSMISSION........................ A-22

Usual Factors.........................................................................A-22

Unusual Factors ..................................................................... A-27

Echo....................................................................................... A-28

RATIO, dB, dBm & dBV.............................................................A-35

BINARY SIGNALS TABLE........................................................ A-39

MAKER CODES TABLE............................................................A-42

STANDARD DOCUMENT SIZES..............................................A-44

G3 FACSIMILE TRANSMISSION CONTROL PROCEDURES A-45

GLOSSARY...............................................................................A-67

INDEX............................................................................................I-1

CHAPTER

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1 BASIC OF TELEPHONE

1. INTRODUCTION TO THE TELEPHONE................................. 1-2

1.1 Parts of the Telephone .................................................... 1-2

1.2 Making a Call .................................................................. 1-3

1.3 How do you make a call? ................................................ 1-4

1.4 Voice Frequencies Carried by the Telephone.................. 1-4

2. STRUCTURE OF A TELEPHONE........................................... 1-5

2.1 Transmitter (Microphone) ................................................ 1-6

2.2 Receiver (Speaker) ......................................................... 1-7

2.3 Voice Circuit .................................................................... 1-7

2.4 Hook Button .................................................................... 1-8

2.5 Dial.................................................................................. 1-9

2.6 Bell (Speaker)................................................................ 1-10

3. TYPES OF TELEPHONES ....................................................1-11

3.1 Dial Telephones............................................................. 1-11

3.2 Pushbutton Telephones................................................. 1-11

3.3 Digital Telephones......................................................... 1-12

4. CIRCUIT DIAGRAM IN THE TELEPHONE ........................... 1-13

4.1 Dial Telephones............................................................. 1-13

4.2 Pushbutton Telephone................................................... 1-14

5. INTRODUCTION TO THE TELEPHONE NETWORK............ 1-15

5.1 Parts of a Telephone Network.......................................1-15

5.2 Basic Structure of a Telephone Network System.......... 1-19

5.3 Nationwide Telephone Network (In case of Japan)....... 1-20

6. TELEPHONE EXCHANGES.................................................. 1-25

6.1 Types of Exchanges......................................................1-25

6.2 The Exchange............................................................... 1-26

BASIC OF TELEPHONE

1–2

1. INTRODUCTION TO THE TELEPHONE

You can’t transmit a document unless your facsimile and the receiving fac­simile are connected over a telephone line. In this section, let’s learn about
the basics of telephones and telephone lines.

1.1 Parts of the Telephone

Very few people know the names of the parts of a telephone even though
they use it every day. Let’s learn the names of the parts on a telephone.

Fig. 1-1 Parts of the Telephone

What we generally refer to as the receiver was in fact the handset.
The “receiver” is the part that we hold against the ear on the handset.
Likewise, the part that we bring near our mouth on the handset is called the
transmitter.
Some people mistakenly refer to the handset as the receiver.

Fig. 1-2 Handset

(Receiver)

(Handset)

(Transmitter)

Hook button

Dial

Pushbuttons

Stopper

Telephone body

Receiver

Transmitter

Receiver

Transmitter

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BASIC OF TELEPHONE

1.2 Making a Call

There are names for the party being called and the party making the call.
When we make a call, one of the two parties must first dial to call up the
other party by the bell on its telephone. Making a call in this way, that is,
dialing is called the “outgoing call”, and the call that arrives is called the
“incoming call”.

Fig. 1-3 Telephone Call State (1)

When you lift the handset, the handset is “off-hook”. When you hang up,
the handset is “on-hook”.
These days, some telephones have an on-hook button. F or e xample, even if
the handset is placed on the telephone body, pressing this on-hook button
sets the telephone to the same state (on-hook) as when the handset is
picked up.

Fig. 1-4 Telephone Call State (2)

Outgoing call Incoming call

Off-hookOn-hook

BASIC OF TELEPHONE

1–4

1.3 How do you make a call?

When you call someone, you must take various actions.
Let’s consider each individual action needed for making a call.

(1) You pick up the handset. This means you are making a calling request.

The telephone exchange gets ready to connect you to your party.

(2) The exchange emits the dial tone to indicate it is ready for the called

number.
(3) You dial your party’s number. This is the dialing signal.
(4) When the telephone exchange receives your dialing signal, it attempts

to connect with your party. If your party is free, the exchange will

make the connection, and you will hear a ringing tone.
(5) When the other party picks up the handset, the exchange stops sending

the ringing tone, so that you can have a conversation.
(6) You have your conversation.
(7) You hang up.

When the called number is in use, the calling party hears a busy tone. Even
if the called party hangs up while the caller is listening, the calling party
will still hear the busy tone. So the calling party needs to dial again.

1.4 Voice Frequencies Carried by the Telephone

The human ear can hear sounds with frequencies between 10 Hz and
15,000 to 20,000 Hz. The human voice is composed of many different fre­quencies. To be able to transmit the full range of hearing over the phone
line would require very high-quality amplifiers and other equipment. Far
more than is practical.
The telephone transmits enough voice frequencies to understand what is
being said; usually between 300 to 3,400 Hz.

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2. STRUCTURE OF A TELEPHONE

A telephone consists of a receiver (speaker), a transmitter (microphone), a
voice circuit, a dial, a bell (speaker), and a hook button.
Of these parts, the parts that play the most important roles are the transmit­ter and the receiver. The transmitter converts human voice to electrical sig­nals, and the receiver converts the electrical signals from the other party to
voice.
Here, let’s learn about the mechanism of these parts and the roles that they
perform.

Fig. 1-5 Handset

Receiver

Transmitter

BASIC OF TELEPHONE

1–6

2.1 Transmitter (Microphone)

The voice vibrates a diaphragm compressing/releasing carbon powder.
When carbon powder is compressed, its contact resistance decreases.
When the powder is released, its contact resistance increases. So direct
current varies corresponding to the change of pressure (voice). This is
called “voice current”. Recently, a microphone is applied to the transmitter
of the telephone.

Fig. 1-6 Transmitter and Voice Current

Carbon powder

Fixed electrode

Diaphragm

Air vibration

Contact
resistance

Voice current

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BASIC OF TELEPHONE

2.2 Receiver (Speaker)

The receiver acts just like an electromagnet. The receiver creates voice
waves by changing magnetic force, which move a vibrating diaphragm
according to the current strength.

Fig. 1-7 Receiver

2.3 Voice Circuit

When the transmitter and receiver are connected as shown in the Fig. 1-8
to make a voice circuit, voice can be transmitted in both directions along
the two wires.

Fig. 1-8 Two-way Circuit (Two Wires)

Armature

Permanent magnet

Diaphragm

R

R

T

T

Calling party Exchange Called party

T:Transmitter
R: Receiver

BASIC OF TELEPHONE

1–8

2.4 Hook Button

When a hook button is closed by picking up a handset, direct current flow s
to the telephone circuits.

Fig. 1-9 Hook Button

The purpose of this is twofold (i) so that direct current is made to flow to
the transmitter to provide current for sending voice when the handset is
picked up, and (ii) so that the exchange detects this direct current to recog­nize that the handset has been picked up.

Fig. 1-10 DC Loop

Picking up a handset is called “making a DC loop”. A DC loop lets the
exchange know that:

(1) The calling party (the party making the call) is ready to call someone.
(2) The called party answered. (The party receiving the call)
(3) The handset is on-hook.

Hook button Hook button

T: Transmitter
R: Receiver
HS: Hook switch

R

T

HS

Exchange Telephone

Direct
current
detector

Detects direct
current.

Closed when a handset is
picked up. (Off-hook state)

Direct current (DC) loop

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2.5 Dial

Dialling enables an exchange to connect one party to a requested number
according to a dialing signal. “DP” means the Dial pulse contact. The con­tact is usually closed. When you turn a dial and release it, the contact
opens the same number of times as the number you dialed. (When the
dialed number is 0, the contact opens 10 times.)
When a DC loop is made as shown in the Fig. 1-11 and the dial returns to
its start position after the number “4” is dialed, the DC loop is cut four
times. This is called the “dial pulse”.
Dialing using this dial pulse is called “pulse dial” due to the fact that num­bers are dialed by this pulse.

Fig. 1-11 Dial Pulse

The exchange selects and calls up the other party by counting the number
of dial pulses.

Dials return to their start position at either of two speeds:

• 10PPS

• 20PPS
PPS (Pulse Per Second) indicates how many dial pulses are generated per
second.

T:Transmitter
R: Receiver

R

T

DP: Dial pulse contact

HS (Off-hook state)

HS: Hook switch

DP

ON

OFF

1

2

3

4

5

6

7

8

9

0

Dial return

DP

OFF

ON

BASIC OF TELEPHONE

1–10

Here, we have described an example (number of dial pulses = N) where the
number of dial pulses is the same as the dialed number (N). However, in
some countries, the number of dial pulses is sometimes different as fol­lows:

The number of dial pulses is the dialed number (N) + 1

The number of dial pulses is the dialed number (N) - 1

2.6 Bell (Speaker)

The calling identification (CI) signal from the exchange for notifying that
you have an incoming call is converted to the ring tone and is output.
Recently, a speaker or buzzer is used instead of the bell.

Dialed number 1 2 34567890
Number of dial pulses23456789101

Dialed number 1 2 34567890
Number of dial pulses10123456789

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3. TYPES OF TELEPHONES

There are three types of telephone: dial telephones and pushbutton tele­phones that are used on analog lines, and digital telephones that are used
on digital lines.
In this section, let’s learn about these types of telephones.

3.1 Dial Telephones

The type of telephone having a dial as explained earlier in section 2.5 is a
dial telephone.

3.2 Pushbutton Telephones

Pushbutton telephones differ from telephones that are operated by turning
a dial in that buttons are pushed to output dialing signals.
Pushbutton telephones have 12 buttons and have an oscillator inside to
generate seven different frequencies. For example, if you push button 1,
two frequency currents, 697 Hz and 1209 Hz, are sent simultaneously. This
is called DTMF (Dual Tone Multi Frequency), and dialing using this
DTMF is called “tone dial” due to the fact that numbers are dialed by this
tone. Dialing is also referred to as PB (Push Button) due to the fact that
buttons are pushed.
The exchange distinguishes numbers by this DTMF.
Of these 12 buttons, the * and # buttons are special buttons, and are used
for selecting various handy communications services.

Fig. 1-12 Pushbutton Telephone

12
4
7

0

98

65

3

697Hz

1209Hz

Mixed signals

(PB signal)

697Hz

770Hz

852Hz

941Hz

1209Hz 1477Hz

1336Hz

BASIC OF TELEPHONE

1–12

Some pushbutton telephones have a dial selector switch for selecting
between tone dialing (PB) and pulse dialing. With these pushbutton tele­phones, if the selector switch is set to pulse dialing, the telephone outputs
dial pulses even though the telephone looks like a pushbutton telephone.

3.3 Digital Telephones

Though digital telephones also have 12 buttons just like a pushbutton tele­phone, the dialing signals are output not as a tone (frequency) but as a code
comprising a combination of digital 0s and 1s. Also, the signals for ringing
the bell on the other party’s telephone are sent as a code comprising a com­bination of digital 0s and 1s.

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4. CIRCUIT DIAGRAM IN THE TELE­PHONE

In this section, let’s learn about the basic circuits inside a telephone.

4.1 Dial Telephones

The Fig. 1-13 shows the basic circuit of a dial telephone.

Fig. 1-13 Basic Circuit of Dial Telephone

However, in actual fact, hook switch HS2 is provided in addition to switch
HS1 on dial telephones as shown in the Fig. 1-14. The bell circuit is closed
and short-circuited by the switch HS2 when the handset is picked up.
Ringing of the bell by dial pulses is thus prevented.
Dial telephones are also provided with a dial shunt contact DS to prevent
noise caused by the entry of dial pulses on the receiver. The DS closes
when you start dialing and opens when the dial has finished returning to its
start position.

Fig. 1-14 Circuit of Dial Telephone

T:Transmitter
R: Receiver
DP: Dial pulse contact
HS: Hook switch

R

T

HS

DP

T:Transmitter

R: Receiver

R

T

DP: Dial pulse contact

HS

1: Hook switch 1

DP

DS: Dial shunt contact

HS

2: Hook switch 2

HS1

HS2

DS

Bell

BASIC OF TELEPHONE

1–14

4.2 Pushbutton Telephone

The Fig. 1-15 shows the basic circuit of a pushbutton telephone.
Basically, the only difference between the circuit of a pushbutton tele­phone and the circuit of a dial telephone is that the dialing signal generator
differs.

Fig. 1-15 Basic Circuit of Pushbutton Telephone

R

T

HS

Bell

T:Transmitter
R: Receiver

HS: Hook switch

12 pushbuttons
and DTMF
generation
circuit

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5. INTR ODUCTION TO THE TELEPHONE
NETWORK

We can talk to people over a long distance because we have an interlinked
telephone network which contains many telephone centers.
In this section, let’s learn about the mechanism of a telephone network.

5.1 Parts of a Telephone Network

To communicate over a telephone line, you need two telephones, a tele­phone line, and an exchange system. The telephone is sometimes called a
terminal, because it is at each end of the telephone line.

Fig. 1-16 Parts of a Telephone Network

Telephone line

Exchange system

Telephone (Terminal) Telephone (Terminal)

BASIC OF TELEPHONE

1–16

To simply connect two telephones without using an exchange, every tele­phone must be connected individually to every other telephone. This type
of network is called a mesh network.

Fig. 1-17 Mesh Network

In a mesh network, you need more telephone lines than telephones.
The number of lines needed to connect telephone is given by n(n-1)/2. (F or
example, you need about 500,000 lines for 1,000 telephones.)
Clearly, it is impossible to connect many telephones in a mesh network.
So, you can see that a telephone exchange is quite necessary. An exchange
connects a line to a telephone when it receives a calling request. In this
system, the number of lines can be equal to the number of telephones ser­viced by the exchange. This network system is called a star network.

Fig. 1-18 Star Network

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BASIC OF TELEPHONE

So far, we ha ve the mesh network and the star network. These are the basic
types of network systems. If we combine both networks into one system,
we have a hybrid network.

Fig. 1-19 Hybrid Network

BASIC OF TELEPHONE

1–18

In this way, a telephone network consists of telephones used as a terminal
for converting voice to electrical signals and electrical signal back again to
voice, a telephone line for transmitting electrical signals to places far away,
and an exchange system for connecting two telephones.
Telephone lines come in various types: coaxial cable, optical fiber cable,
microwaves communications satellites and submarine cable.
The places where the exchange system is located is called the telephone
center (or the exchange center).

Fig. 1-20 Telephone Network Organization

Telephone

Transit
exchange

Subscriber
exchange

Telephone

Transit
exchange

Subscriber
exchange

Microwaveradio relay system

Satellite
communication
system

Optical fiber cable/

Coaxial cable system

Electrical signal

Voice

Electrical signal

Voice

Transit trunk

Subscriber line

Submarine
cable system

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BASIC OF TELEPHONE

5.2 Basic Structure of a Telephone Network System

As the number of telephones to be connected to the exchange increases
and the conversation area expands, it becomes more economic to set up
two or more exchanges and connect between exchanges by telephone lines
rather than terminating all of the telephone lines in a single exchange.
The line connecting two exchanges is called a transit trunk.
The line connecting an exchange and a telephone is called a subscriber
line.

Fig. 1-21 Subscriber Line and Transit Trunk

As the number of telephone centers increases, it becomes more economic
to set up an exchange for terminating only the transit trunks and connect­ing this exchange in the center in shape of a star rather than connecting
telephone centers to others in the shape of an interlinked network by
directly connected transit trunks.
This kind of exchange is called a transit exchange. An exchange that con­nects subscriber lines is called a subscriber exchange.

Fig. 1-22 Transit Exchange System

Exchange

Subscriber line

Transit trunk

Transit exchangeSubscriber exchange

Without a transit exchange (Mesh) With a transit exchange (Star)

BASIC OF TELEPHONE

1–20

As the transit exchange relay-switches conversations between subscriber
exchange, we can consider transit exchange to be ranked (classified)
higher than the subscriber exchange. The rank for an exchange is called the
grade, and the telephone center is called the center grade. That is, the high
grade exchanges can route calls to a wider area.

Fig. 1-23 Center Grade

5.3 Nationwide Telephone Network (In case of Japan)

The nationwide network in Japan can be divided into subscriber areas
matched with administrative districts. A subscriber area has more than one
subscriber exchange to connect all the telephones in the area.
A call within the area is called a local call, and can be made by dialing an
exchange number and the subscriber number.

Fig. 1-24 Subscriber Area and Local Call

Transit exchange

Subscriber exchange

Telephone

Exchange

Local call

Subscriber area

1–21

1
2
3
4
5
6

ït

çi

BASIC OF TELEPHONE

A call made between subscriber areas is called a long-distance call, and
can be made by dialing an area code, an exchange number, and a sub­scriber number.

Fig. 1-25 Subscriber Area and Long-Distance Call

The network for local calls is the local network. And the line and the
exchange for these calls are called the local line and the local exchange.
The network for long-distance calls is toll network. And the line and the
exchange for the long-distance call are called the toll line and the toll
exchange.
A toll exchange is classified into three ranks: toll centers, district centers,
and regional centers.

Fig. 1-26 Structure of Telephone Network

• Regional center (RC)

RCs have been established in Sapporo, Sendai, Tokyo, Nagoya, Kanazawa,
Osaka, Hiroshima, and Fukuoka.

Subscriber
exchange

Subscriber area A Subscriber area B

Long-distance call

Subscriber
exchange

End office (EO)

Subscriber

Toll line

Local line

Toll center (TC)

District center (DC)

Regional center (RC)

BASIC OF TELEPHONE

1–22

• District center (DC)

DCs have been established in every seat of prefectural government of the
same rank city.

• Toll center (TC)

TCs have been established at central towns in a district center area.

• End office (EO)

An end office (EO) is an office that connects telephones in a subscriber
area.

5.3.1 Local telephone network

The subscriber area has one end office, which connects all the telephones
in the area. In this case, the subscriber area is called a single office area.

Fig. 1-27 Single Office Area

As the number of telephones increase, there will also be an increase in the
number of end offices called branches. These branch offices are connected
in a mesh network. In this case, the subscriber area is called a multiple
office area.

Fig. 1-28 Multiple Office Area

Subscriber area (Single office area)

I'm a single
office.

Subscriber area (Multiple office area)

We are

multiple

offices.