1D. Telephone Basicspdf

7/29/2019 1D. Telephone Basicspdf

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COMMUNICATION SYSTEM

REVIEW

TELEPHONE BASICS

PBX Block Diagram

2

Internal

Switching

Matrix or

Network

Internal

Switching

Matrix or

Network

Line/Loop

Interface

Trunk

Interface

Control

Processor

(CPU, RAM

etc.)

Line/Loop

Interface

Line/Loop

Interface

TrunkInterface

Trunk

Interface

More

not shownMore

not shown

Multiple station loopsMultiple T-1 trunk groups

optional

remote

line

concen-

trator


2/172

Simple PBX

3

Extension to Extension Call

(Internal Call)

4

1. Station comes off hook

2. Line circuit notes origination

3. Control detects origination, check

line class-mark

4. Control finds free signaling

receiver5. Control finds and sets up a path

from line to receiver

6. User hears dial tone, starts

dialing/signaling

7. Dial tone is removed, digits are

accumulated

8. Control examines dialed number:

Find called line

Check for busy, hunt group,

call forwarding, pick-up group


3/173

Extension to Extension Call

(Internal Call)

5

9. Control finds and sets up path,

caller to ring-back tone

10.Finds and sets up path, called

phone to ringing

11.Monitors for answer or abandon

12.Called party answers; control

detects answer at line circuit

13.Control finds and sets up calling-

to-called talk path

14.Monitor for flash and/or hang-up

Basic Telephone

6

ear

T

R

mouthDTMF

ringer

C

dial switch

SLIC

Telephone

Subscriber

Line

CO

(Local Exchange)

cradle switch

off-hookon-hook

tip (+)

ring (-)

Thisimage cannot currently bedisplayed.


4/174

Basic Telephone

7

Basic Telephone

8


5/175

Subscriber Line Interface

9

hybrid

TTelephone

current

detector

~

ring switch

ring

generator

(100Vrms 25 Hz)-48 VDC

Subscriber

Line

crossconnect

switch

Subscriber Line Interface Circuit

Processor

control channel

Call Statesidle on hook

dialing dialing in progress

calling after dialing

ringing incoming call

called call in progress

tip (+)

ring (-)

Battery Supply Feeding of subscriber handset

Over-voltage Protection for electronic components

Ringing Ringing current to subscriber

Signaling Recognizing dial digits

Coding Analog/digital conversion

Hybrid 2-wire/4-wire conversion

Test Access testing of subscriber lines


10


6/176


11


MT91600

12


7/177

Tones

13

DTMF Receiver MT8870

14


8/178

DTMF Receiver MT8870

15

Switching Matrix CD22100

16


9/179

Control

17

Outgoing Call

18

1. Station comes off hook

2. Line circuit notes origination

3. Control detects origination, check

line class-mark

4. Control finds free signaling

receiver5. Control finds and sets up a path

from line to receiver

6. User hears dial tone, dials trunk

access code

7. Dial tone is removed, access

code is received

8. Control examines access code:

Check against line class mark

for restriction

Looks for free trunk group


10/1710

Outgoing Call

19

9. Control finds and sets up path,

from the line to the selected trunk

10.Control causes trunk to send

seizure toward CO

11.CO responds with dial tone to the

caller; caller dial called number

12.Dialed number goes to the CO to

set up the call, and the digit

receiver to check restriction

13.Control examine access code, if

any, and office code, if necessary.

Compare them with the list in

memory

14.Call is permitted. Drop path to

signaling receiver

15.Monitor line for flash and/or hang-

up, monitor trunk for hang-up

Incoming Call to Attendant

20

1. CO seizes trunk, rings; trunk

detects ringing

2. Control detects seizure at trunk;

checks trunk class marks

3. Control activates lamp, sounder

at console4. Attendant accepts call, signals

control

5. Control finds, sets up a trunk

switched-loop path

6. Ringing from CO is tripped,

answer supervision returned

7. Attendant greets caller; obtains

called extension identity


11/1711

Incoming Call to Attendant

21

8. Attendant keys in called

extension

9. Control examines dialed number:

Finds called line

Check for busy, hunt group,

call forwarding, pick-up group

10. Finds and sets up path to ring-

back tone, ringing, drops

switched loop

11.Monitor for abandon or answer

12.Called party answers

13.Answer is detected, ringing is

tripped

14.Control finds and sets up a talk

path

15.Control monitor for flash and/or

hang-up

Trunk Interface

22


12/1712

Analog Trunk Interface

23


24


13/1713


25


26


14/1714

E&M Trunk Interface

27

Basic Digital PBX

28

SLIC

PCM

MUX

Hybrid

SLIC

TDM

port

TDM

port

TDM

port

TDM

port

Tone

&Ann

DTMF

decode

Processor

Subscriber

Lines

Hybrid

2w4w

DXC

E1/T1E1/T1


15/1715

Digital Trunk Interface

29


30


16/1716


31


32


17/17


33

Time Slot Interchange

34

Documents

1D. Telephone Basicspdf