Telephone System
By : Warsun Najib
Telepon System Concept



Telephone network is often called as PSTN (Public Switch
Telephone Network)
Telephone Device
Central Office (CO)
suatu istilah untuk menggambarkan pusat jaringan telepon (dalam
suatu kota). Tugasnya menyediakan daya untuk telepon, me-routing
panggilan, merekam tagihan telepon, dsb.

Trunk (E1)


Link/kabel between CO to other CO
Local Loop
Pasangan kabel telepon yang terhubung antara central office dan
pesawat telepon rumah (kantor).

Switch
Perangkat yang me-route komunikasi ke bagian (tempat) yang lain.




Pada awalnya, switch terbuat dari banyak switch-switch mekanik
Saat ini, mayoritas switch adalah elektronis, bahkan digital.
Digital switches lebih reliable, dan menawarkan banyak keuntungan
Distribution Network


MDF
Rumah Kabel
Telephone Set
Hook Switch
2
Speaker
Mic
Hibrid
•Pemisah mic
dengan speaker
•Penekan nada
samping
1
Dialer
Bell
Standby : Hoook switch is on position 1, Idc from CO does not come, Ringing
signal (ac) can activate Bell
Busy : Switch is off-hook (hook-switvh on position 2),
Telephone : Off-Hook / Busy
H
D
Side Tone
Dialing System
DTMF (Dual tone multi frequency)
 Rotary Switch

Dual Tone Multi-frequency
Kolom 1
Kolom 2
Kolom 3
[1209 Hz] [1336 Hz] [1477 Hz]
Baris 1 [697 Hz]
1
2
3
Baris 2[770 Hz]
4
5
6
Baris 3[852 Hz]
7
8
9
Baris 4[941 Hz]
*
0
#
DTMF
i(t)
Digit ‘1’
Digit ‘6’
space
T
T
t
Periode T > 100 ms depend on how fast finger push
the button (normally 250 ms)
Dialing : Rotary Switch
‘1’ one stop pulse
0
9
8
‘2’ two stop pulse
7
‘3’ three stop pulse
…
6
‘0’ ten stop pulse
5
4
3
2
1
Rotary switch dialing system
i(t)
Dial a number
Off-hook
‘3’
space
‘2'
t
0
T/3
T :100 ms
≥ 4T
Subscriber link signal (Link Voltage)
Volt
Bell, ringing
voltage
100
50 On-hook Off-hook
Dialing
pulse
Incoming
0
-50
48 V
-100
-150
voice
I:16-20
mA,
Δv: 48 V
6-8 V
ingoing
Outgoing
0,5-1 V
1-2 V
ΔI: 18 mA
20 Hz, 90 Vrms,
2 s on, 3 s off
Switching Element
Central Office
trunk
SLIC
SLIC
To/from
other CO
trunk
Switching Device
SLIC
Pengisyaratan
Controller
register
Controller can be :
•Sentralized
•Distributed at signaling and switcing Device
Pengisyaratan
SLIC : Subscriber Line
Interface Circuit
Switching System
Step By Step,
Each digit activates directly one
switching-level, except the last 2
digit usually connected to 2dimension switch
3
Call
Switch
Finder level 1
3054
0
5
Switch
level 2
Switch
level 3
4
Switch
level 4
Illustration of Call Switching
Common Control

Each digit of dialed number is first stored
in a register at CO, then if the destination
number is not busy, call is routed to the
phone.
Switching Process of Telephone Call
Caller lift handset / off hook
CO find the available link
Get a link
No
Yes
CO send dial-tone to caller
Caller dial the destination number
CO make switching process
yes
Is dialed number
free (not busy) ?
CO send busy tone
to caller phone
CO send:
•Ringing signal to dialed phone
•Ringing tone to caller phone
(tuut – tuut…..)
Called phone
Off hook
yes
Call success
no
No
Call drop
Voice Signaling
Nama Signal
Off-hook
Kegunaan
Memberitahu CO bahwa user
ingin melakukan panggilan
Dial tone
Memberitahu user bahwa CO
sudah siap melayani (ready)
Ringback tone
Memberitahu user bahwa
telepon tertuju sedang
berdering
Ringing voltage Tegangan tertentu yang
dikirim untuk membunyikan
bel
Busy signal
Memberitahu user bahwa
telepon tertuju sedang sibuk
On-hook
Memberitahu CO bahwa user
Private Branch eXchange
.
.
.
Common
Subscriber
m ext-link
CO
2201
.
.
.
n main link
2202
1302
PBX
90XXXX
Operator
PBX is categorized:

PMBX private manual branch exchange


Both intern and extern call is handled by an operator
PABX-private automatic branch exchange


Intern call is automatic
Extern call



If n >1 (link between co-pbx)



Automatic if the device has DID (direct inward dialing)
Via operator If device does not have DID
User call via one number if PABX has hunting system
User can call via n different number if PABX doesn’t have
hunting system.
Advantage of PBX


Cost
Probability of success call
Numbering System
Open System
 Close System

Network from CO to Subscriber
LE
Primary network
-
MDF
CCP
CCP
MDF 2000 pairs
CCP 50 pairs
DP
DP
DP:10 pairs
DP
PBX
Secondary network
MDF,CCP,DP are in a form of cable switching terminal
Network Between LE
Regional
Central
Toll
Central
Regional
Central
Toll
Central
LE
yk1
LE
yk2
One local area
Toll
Central
LE
yk3
Toll
Central
Toll
Central
LE
LE
Toll
Central
LE