Unit 1 :TELEPHONE SWITCHING AND SIGNALLING

contains

exchange

signalling

SPC switchin

g

Swtiching

network

Interprete and describe the basic principles and functions of exchange.

Recognize switching network and the term "concentrator",

"distributor", "EXPANDER", and "multiplex“.

Draw and label a block diagram of SPC switching.

Identify and describe the signaling principles.

i. the type of signaling.

Ii. the type of signal in the signaling between exchanges with

customers.

Iii. the type of signaling between the exchanges with the

exchange.

Objectives :

Tele comes from the Greek word that is long distance,

while Foni is defined as sound or speech.

Telephony communication means the transmission of speech

at long range, where in the wave transmitter

voice changed to the form of electrical signals and then

the signal is converted back to wave

voice.

Introduction:

Frequency bandwidth used for telephony services is

300 - 3400 Hz frequency which is a human voice.

Therefore, all telephony equipment and line connections between the

devices must be able to communicate in the bandwidth.

Is a center where all the phone lines can be connected to enable communication speech is achieved.

The equipment in exchange functions as a switch for easy connection process.

Now, most of the exchanges is the type GSC (Group Swicthing Centre)

Exchange :

PPU - Main Switching Centre (MSC) PPZ - Switching Centre Zone (SCZ)PPK – Switching Centre Areas PPT – Local Switching CenterP – Customers - two wire cable

PPU

PPZ PPZ

PPK PPK PPK PPK

PPT PPT PPT PPTPPT PPT PPTPPT

P P P P P P P P P P P P P P P P

Rajah : Hiraki Kebangsaan

International

exchangeLocal

exchange TandemExchange

3 types of exchange

Available in a same area

Connecting two or more local exchanges and its main

features is not connected to the customer.

Exchanges and tandem exchanges connecting to

the nation

Function of exchange

Record the customer’s meter reading (time, no.telefon called)

Overseeing the process between the client and exchange switching

Record customer demand- Provides no. telephone, cut meter for temporary condition

Provide supervisory signals (dial tone, ringing, busy tone interference)

Control the quality of conversations and recorded service quality of exchanges .

Switching Network.

Some of the required switching are:-

Concentrator ( Penumpu)

Distribution ( Pengagih )

Expander

Multipleks ( Multiplexer )

The combination of these networks can create complete Public Switching

Telephone Network (PSTN).

Macam mane nak sambung??

Concentrator ( Penumpu )

Concentrator (Penumpu)

distributors

Customers

Permanent circuit connections made in this network.

Concentrator unit is controlled by the local switching exchange directly.

The concept of traffic in the PSTN network

Advantages of concentrator are:-

►Able to handle thousands of users at the same time.

►Line can reduce the cost of repeated use, repeater and others.

Distributor ( Pengagih )

►The distributor (distributor) is a device between the concentrator (concentrator) and expander. This device is connect thousands of users in the PSTN network in stages.

 ► Where, about 1000 local line will enter the off-line and only produce 100 output. Next, each distributor can handle 100 online from the concentrator.

► Then, the line from the distributor, will enter the EXPANDER.

distributors

Expa

nder

Local line 1

Local line1000

Local line 1

Local line1000

Output channel

input channels

conc

entr

ator

Switching network of PSTN

Expander

This returns the number of units of the original line into the

concentrator.

From the distributor, all the 100 line will enter the EXPANDER and

reissue of 1000 online consumers in the destination separately.

  EXPANDER and off the switching process depends on number of

lines that is activated simultaneously.

Multipleks ( multiplexer )►This device is a tool that can reduce the number of cabling to be used in a process of signal transmission and receiving information.

►This may be achieved by combining several input signals and produces an output only.

►This combination technique known as multiplexing (multiplexing). ♣ Time Division Multiplexing (TDM) ♣ Frequency Division Multiplexing (FDM).

►Demultiplexing - separating the information to the original signal.

MULTIPLEXING AND DEMULTIPLEXING TECHNIQUE

MU

X

Signal Information 1Signal Information 2

Signal Information 10

DEM

UX

Signal Information 1

Signal Information 2

Signal Information 10

Switching

It is a process of connecting customers from one location to another through the exchange as the medium of communication.  Switching functions: ►provide services in facilities known customers. ►when more sophisticated switching system it serves to provide additional facilities that enable communication network to provide better service to consumers, and overseeing the operations and maintenance.

TYPES OF SWITCHINGStep by

step The main process through the development of telephone calls made through a tone switching step of dialed digits.

The problem of switching step by step:►Power : requires a lot of power to move the switch for call processing

component. ►Space : The components of the main switch is made from brass, copper, and magnetic pressure is very heavy and require steel in the floor where they are fitted. ►Maintenance: a lot of moving parts in a switch requires cleaning dirt and oil to facilitate the communication is made in the switch. ►Noise: communication through physical path be adjusted via the switch for call processing.

CROSSBAR

► Crossbar switching is an improvement from switching the step-by-step (switching strowger)

► Switching process performed by the relay (pet clothing).► Consists of vertical and horizontal line.► Require connection to a combination of two lines.► This system has a horizontal switch used to select vertical

switch. Horizontal switch function to hold the vertical switch.► Other names called switching

matrix.

Stored Program Control

Merupakan kaedah pensuisan ibusawat telefoni Ia menggunakan kawalan komputer untuk memproses

panggilan daripada pengguna secara automatik. Operasi komputer berpandukan aturcara yang telah

ditetapkan. Sistem dalam bentuk modular iaitu terdiri daripada

subsistem Sistem menggunakan ‘common channel signalling’ (CCS) Sistem menggunakan ‘time switch’

SPC switching block diagram

SPC switching block function

memory♣ Keep status of activities of users in software form.

Director of the control (control director)♣ Programs that control and direct the entire system.

File ♣ Store information of user charges.♣ Provide special schedules for special services or other services.

DTMF (decodic)- Decoding signals produced during the process of dialing

Scanner ♣ Track the status of algae line telephone and cellular signaling.

Drivers ♣ Connect and disconnect the circuit.♣ Provide access to the dial tone signal and the signal.

CPU (central processing unit)♣ Control and programmed to execute the program.

Tone generator ♣ Generate a notification signal or a call sign.

SPC operating process

1. A caller picked up the telephone handle, A-line caller is activated and can be detected by the scanner.

2. CPU will detect and obtain location information, time and so when the caller A pick up the phone handle.

3. Information send to memory for storage.4. Thereafter, the CPU will connect the caller A with switching path

'X' through the drive.5. Dial tone is sent to the caller A from dial tone generator.6. A caller entered digits dialed numbers, a dial tone generated by

the DTMF stopped.7. CPU identifying type of call and destination of the call.

8. Drivers will drive the switching devices 'X' to provide access to the for caller A with caller B.

9. CPU provides instruction on tone generator to send ringing tone for caller B and caller A.

10. Once the handle of caller B is lifted up, the scanner will detect the phone picked up and sent to the CPU.

11. After that, the CPU directs tone generator to stop ringing and start recording the time and location of the call.

12. After the conversation ended, whether the caller A or B put handle, the scanner will detect the emission signal and sent to the CPU.

13. CPU will provide the bill (payment) and the records are stored in files.

Advantages of SPCo Maintenance and monitoring is easy because the method

of exchange operations may be varied by changing the stored program control at any time.

o Signaling from the exchange can be handled easily and effectively.

o Increase in line do not need additional signaling device.o Low maintenance costs.o The process is much faster than manual methods.

Disadvantages of SPC

Minor damage can lead the exchange operations to stop.

Ensure that employees trained on new techniques and methods of handling.

Maintenance of over-reliance on suppliers. Service requires additional building equipment

such as air-conditioned room and the program.

SIGNALLING

Signaling is defined as a transfer or change of address or information between different parts found in a telecommunications system.

Division involved in the signaling:►Callers to the exchange►Exchange with an exchange►Exchanges with the so-called

Signaling method between the caller or the called exchange

Among the callers to exchange

Signal Type Definition

grab signal(seizure) Signal when the handle lifted(off-hook)

Signal ‘clear forward’ Signal when the handle are placed(on-hook)

Signal ‘address’ Dialing pulses to exchanges

Among the exchange to the caller

Among recipient to the exchange

Signal Type Definition

ringing signal Signal indicates an incoming call

Signal Type Maksud

answer signal When the recipient pick up the handle (off-hook)

Signal ‘clear back’ When the recipient put the handle (on-hook)

The signal from the exchange to the caller or the receiver(standard service tones)

Jenis nada Maksud

Dial tone The resulting tone on the caller after caller lift the handle. Prolonged sound tone. (example: tuuuuuuuu ....)

Busy tone Tone to be received by the caller when the number dialed is in use. (example: tuut, tuut, tuut ....)

Tone no number A voice message will be generated when the dialed number not in service.

Ringtones Tone is received by the caller when a call is succesfully connect. (example: tuut tut, tut tuut, tut tuut .....)

Method of signaling between exchange to exchange

Channel Associated Signaling,(CAS)

Common Channel Signaling (CCS)

Voice signals and control signals are sent on the same channel or circuit

Voice signals and control signals are sent through different channels

Controlled by digital or non digital exchanges Controlled by computer

Signaling speed is low Signaling speed is faster

Exchange A Exchange Btraffic circuit

Transmitter or Receiver Signaling

Exchange C Exchange Dtraffic circuit

Signaling line

Transmitter or Receiver Signaling