PSTN - Public Switched Telephone Network

hello and this is sunny welcome back

today my topic is a public switched

telephone system or PSTN PSTA is the

worldwide collection of interconnected

public telephone network that was

designed primarily for analog telephone

calls is also referred to as the

landlines or plain old telephone service

pots the PSTN is a circuit switched

Network a dedicated circuit is

established for the duration of a

telephone call this contrasts with a

packet switching networks such as the

Internet in which messages are divided

into packets and each packet is a send


originally the PSTA was only an analogue

system but it is now almost entirely

digital only the very oldest and most

backward parts still use analog PSTN

uses signaling system number seven as as

a seven as a signaling protocols in

telecommunication signaling is the user

with signals for controlling

communications in our DB composition we

use a signaling - for example we would

give some signals when we want to start

up a conversation with another person

either by walking closer not too close

or by seeing something when we want to

enter the conversation we would say it

was really a pleasure to talk to you or

I have to go now or simply give them a

dirty look just killing all these

signals or body language is a signaling

system for people as a semi is used to

set up and terminate a telephone call it

also handles caller ID call waiting

voice message or any other features

except the composition itself

you could say that PSTA is all about

switching when a call is made switches

at a different levels create a fixed

path circuit between two telephones

there are five classes of asaji

telephone switches now let's take a look

at them one by one at a different levels

at a very basic level is the customer

premises which include home and a

business telephone subscribers there are

the PSTN uses large organization with 40

or more employees usually go with a PBX

private branch exchange PBX is a

combination of a software and hardware a

PBX allows all the phones in the

organization to be connected internally

and externally with wide range of

services such as caller ID call transfer

groovey call call forwarding voice

message call waiting and etc the PBX is

connected to your local exchange or

central office a classified telephone

switch the distance between telephone

users and local exchange is called local

loop or last mile the local exchange

connects with the backbone of PSTN by

communicating with a classic for

telephone switch tow Center or tandem

office tow Center switches between

several local offices telephone calls

through this Center often involves an

actual cost

that's why class force which is called

tow center Class III telephone switch is

a primary Center which connects class

afford host centres downward and it

connects up with class to sectional

centers which provide interstate or

inter preventional connections for

national long distance course class one

telephone switch and an international

gateway manager domestic cause to other

countries it is where international

cause takes place in summary PSTN is a


worldwide connected telephone network

the PSTN topology and a class level

might be different in a different

countries but the original design was

only for circuit switching analog

telephone calls Nala days the backbone

of the PSTN is mostly digital but most

local looks are still using analog

technologies in terms of physical media

PSTA is a mixed about copper wires

cables fiber optics and wireless PSTN

forms a basic foundation and a very

important part in the infrastructure of

one technologies I hope this video is

helpful thank you very much and see you

next time

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