Toa EXES-6000 Leitfaden

TOA

EXES-6000

SYSTEM

TOA Corporation

KOBE, JAPAN

PREFACE

This booklet readily explains a working principle of the EXES-6000

system from a standpoint of the entire system and so, does not refer

to the details of the circuits, CPU's or IC's. It is compiled with an

emphasis placed on the descriptions of audio and dial signal flows that

are a base of the system, and the timing of their relative switches,

which are explained by using block diagrams of actual circuits. The

booklet is so compiled that the basic items considered necessary,

such as link, PAM, time division switching, etc. are first explained priot

to entering into the explanations of the actual systems with the aim of

making readers knowledgeable on the system by degrees.

TABLE OF CONTENTS

I. BASIC ITEMS

1. Hands-free System

1-1. Basic Principle of the Hands-free System

1-2. Voice Switch

2. Concept of Speech Link

2-1. Manual Exchange

2-2. Crossbar System

2-3. Space Division and Time Division Methods

3. Principle of Time Division

3-1. RAM (Pulse Amplitude Modulation) Signal

3-2. PAM Signal Generating Process

3-3. Demodulation of PAM Signal

3-4. Sampling Pulse

4. Principle of Time Division Multiplex

4-1. Time Division Multiplex

4-2. Access to Time Division Multiplex

4-3. Time Division Exchange

II. VOICE SIGNAL AND DIAL SIGNAL FLOWS

1. Voice Signal Flow

2. Dial Signal Flow

3. Dial Signal Receiving System

4. Line Memory and Signal Memory

III. VOICE SWITCH CIRCUIT

1. Operation Principle of the Voice Switch Circuit

1-1. Hands-free to Hands-free Mode

1-2. Handset to Hands-free Mode

1-3. Handset to Handset Mode

2. Performance Comparison between New and Old Voice Switches

2-1. Voice Switch Features of Duplex Line Unit for the EXES-5000, the EXES-1000 and the EX-16

2-2. Voice Switch Features of Duplex Link Unit for the EXES-6000

IV. PAGING SIGNAL FLOW

1. Paging System and Signal Flow

1-1. Paging by an External PA Amplifier (Zone Paging)

1-2. Station (Group) Paging

1-3. Block Diagram of Paging Interface (PI) Unit

1-4. Paging Signal Flow

2. Connection for Station Paging (Group Paging)

V. PRINCIPLE OF CONFERENCE FUNCTION

1. Example when One Station is in Conference

2. Example when Two Stations are in Conference

VI. TIE-LINE SYSTEM

1. Dial Signal Flow

2. Voice Signal Flow

VII. DATA TRANSMITTING AND RECEIVING SYSTEM

1. Function Setup

1-1. DIP Switch Setting for the Data Transmitting Unit

1-2. DIP Switch Setting for the Data Receiving Unit

2. Principle of Data Transmitting and Receiving System

VIII. TROUBLESHOOTING

GLOSSARY

Page

1~9

2,3

4,5

6~9

6,7

8,9

10~18

10, 11

17, 18

19~24

20~23

21,22

25~33

25~30

26,27

28-3 0

31~33

34, 35

36~3 9

36, 37

37~39

40~50

41~47

41~45

46,47

48~50

51~54

55~59

13~16

1. Hands-free System

1-1. Basic Principle of the Hands-free System

Fig. 1 shows a basic principle of the hands-free

system that permits duplex conversation to be

made between the calling and called parties

without using their hands to lift their station

handsets.

Feedback produced between the microphone and

the speaker by the following reasons, however,

makes it impossible for the system to be in actual

use:

a) Both the speaker and microphone are housed

in a small case, causing them to be located in

close proximity to each other.

b) Speaker audio output level is high.

c) Microphone is very sensitive.

Fig.1 Hands-free System

1-2. Voice Switch

To make the hands-free half-duplex conversation

possible by preventing occurrence of such

feedback problem, Toa EXES-6000 system uses

voice switch in its exchange that is able to detect

signal strength information from both lines and to

automatically select the speech line of higher

signal level, while disconnecting another speech

line of the lower signal level. See Fig. 2.

Fig.2 Principle of the Voice Switch

I. BASIC ITEMS

2. Concept of Speech Link

2-1. Manual Exchange

Fig.3 Manually Operated Exchange (8 lines/2 links)

Fig. 3 shows the simplest telephone system.

When an attendant connects between 2 stations

with a strap, speech path can be set up between

them. The strap represents a link, and the number

of links can be increased as the strap increases in

number. You may presume that the attendant

functions as switch in this system.

2-2. Crossbar System

Fig. 4 shows the crossbar method which corres-

ponds to space division method in the classifica-

tion of speech path. The space division method is

mentioned in the next section 2-3. This method,

however, has both the advantage and the dis-

advantage; the advantage is that all stations in a

system can participate in the conversation at the

same time, while the disadvantage is that an

increase in the number of stations will require

greater number of switches as is evidenced by an

example of the EXES-6000 system with 128

stations where the required number of switches

totals

128

– 128 = 16,256 pieces.

Fig.4 Crossbar System Exchange (8 lines/full links)

— 2 —

2-3. Space Division and Time Division Methods

a. Space Division Method

Fig.5 Space Division Method (8 lines/2 links)

The method employed in Toa EX-16 system. With

this method, the system can do with the relatively

small number of switches if it is the small system.

But if the system consists of many stations, more

switches are required than with the time division

method referred to in the next section. Supposing

the EXES-6000 system (128 stations/16 links) was

designed with this method, it would require (2 x

128) x (16 x 2) = 8192 switches in total.

b. Time Division Method

Fig.6 Time Division Method (8 lines/2 links)

The method adopted in the EXES-6000 system.

All stations are connected by one of each of

transmitting and receiving bus lines, we call

"highway", and the speech signals are multi-

plexed on the bus lines by means of pulses of

different timing. If we compare this method with

the space division method by taking the same

example of the EXES-6000 system (128 stations/

16 links), the required number of switches is 128

x 2 + 16 x 4 = 320 pieces (this is the actually

required number and not in agreement with a

calculation made from the above Figure. For

details refer to later explanations.), which is far

smaller than that required with the space division

method.

— 3 —

3. Principle of Time Division

3-1. PAM (Pulse Amplitude Modulation) Signal

In order to convert an analog signal such as

speech into a pulse stream, a circuit must sample

it at periodic intervals. The amplitude of the pulses

sampled is proportional to the amplitude of the

original signal at the sampling instant. This pro-

cess is called Pulse Amplitude Modulation or

simply PAM.

3-2. PAM Signal Generating Process

Fig.7 Waveforms for PAM Signal

After being modulated by the sampling pulses

having periodic intervals (Fig. 7-(b)), the analog

signal (Fig. 7-(a)) is converted into such PAM

signal as is shown in Fig. 7-(c). However, the real

pulse intervals are so short that the "spurious"

original analog signal in Fig. 7-(c) and the original

signal in Fig. 7-(a) are almost identical.

Fig. 8 shows the PAM signal generating process.

In its block diagram, the analog signal (Fig. 7-(a))

applied to the input is chopped by the ON and

OFF operation of the switch. The switching is

controlled by the sampling pulses with their high

level causing the switch on and their low level the

switch off. Through this process, the PAM signal

(Fig. 7-(c)) is delivered to the output.

Fig.8 PAM Signal Generating Process

— 4 —

3-3. Demodulation of PAM Signal

Both holding capacitor and lowpass filter are

necessary to demodulate the PAM signal.

(1) PAM signal potential of Fig. 9-(1) at each

sampling instant is held with the holding

capacitor.

(2) Sampling pulse elements contained in the

waveforms of Fig. 9-(2) are eliminated through

the lowpass filter.

(3) Through processes (1) and (2), the PAM signal

is demodulated into such a waveform as is

shown in Fig. 9-(3) which is identical with the

original analog signal.

3-4. Sampling Pulse

If a band-limited signal is sampled by pulses

having regular intervals of time and a frequency

equal to or higher than twice the highest signifi-

Fig.9 Demodulation of PAM Signal

cant frequency, then the sample contains all the

information of the original signal.

— 5 —

4. Principle of Time Division Multiplex

4-1. Time Division Multiplex

The time division multiplex is a method to divide

various signals by time and to place such ti-

me divided signals on a single common line called

highway.

Fig. 10 Time Division Multiplex

4-2. Access to Time Division Multiplex

In Fig. 11-(a) at the right hand side, consider just

how many lines are needed to transmit 4 different

signals A, B, C and D to the outputs 1, 2, 3 and 4,

respectively.

(1) The simplest way is to connect between them

as indicated by dotted lines in Fig. 11-(b) at the

right hand side. This method, however, in-

volves such problem as that the more diffe-

rent signals are used, the more grows the

number of lines.

Fig.11-(a)

Fig.11-(b)

— 6 —

(2) Another connection example like one in Fig.

11-(c) can be considered when you wish to

develop the previous connection in order to

reduce the number of lines. The idea of this

connection is that switches 1 and 2 are

synchronized with each other, through which

signals A to D are transmitted in this order to

each corresponding output. In this event, the

signals delivered to the outputs 1 through 4

are the RAM signal described in section 3-2.

(3) In the example of Fig. 11-(c), one switch has

many contact points, but an actual system

uses an analog switch as shown in Fig. 11-(d),

instead of each contact point so that an

individual pair of analog switches (x and y) is

sequenced in the following order:

When the analog switches x

and y

synchro-

nized with each other are on, the signal A is

allowed to go through to the output 1, and

likewise when x

and y

are on, the signal B is

delivered to its corresponding output 2. This

continues till the signal D is sent out to its

output 4, and is again repeated from the

beginning.

Here we show the timing of each switch used in

the system of Fig. 11-(d).

Fig.12 Timing Chart

In the above timing chart, 4 different PAM signals

of Fig. 11-(d) are on a highway (H W line), the state

of which is called "being time division multi-

plexed". In Fig. 11-(d), the signals are quadplexed.

Also, the frequencies (time intervals) of sampled

pulses (i) through (iv) are all the same, which are

the sampling frequency described in section 3-4.

Fig.11-(c)

Fig.11-(d)

— 7 —

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