PSTN in data communication

-

 Public switched telephone network

PSTN  is the worldwide collection of interconnected public telephone network that was designed primarily for analog telephone calls.

PSTN is also referred to as the landlines / plain old telephone service -- POTS.
This is the system that has been is general use since the late 1800's.

Properties of PSTN
  • It is also known as Plain Old Telephone Service (POTS)
  • It has evolved from the invention of telephone by Alexander Graham Bell.
  • The individual networks can be owned by national government, regional government or private telephone operators.
  • Its main objective is to transmit human voice in a recognizable form.
  • It is an aggregation of circuit-switched networks of the world.
  • Originally, it was an entirely analog network laid with copper cables and switches.
  • Presently, most part of PSTN networks is digitized and comprises of a wide variety communicating devices.
  • The present PSTNs comprises of copper telephone lines, fibre optic cables, communication satellites, microwave transmission links and undersea telephone lines. It is also linked to the cellular networks.
  • The interconnection between the different parts of the telephone system is done by switching centres. This allows multiple telephone and cellular networks to communicate with each other.
  • Present telephone systems are tightly coupled with WANs (wide area networks) and are used for both data and voice communications.
  • The operation of PSTN networks follows the ITU-T standards.

How Do PSTN Phone Lines Work?

Step #1 – Your telephone set converts sound waves into electrical signals. These signals are then transmitted to a terminal via a cable.
Step #2 – The terminal collects the electrical signals and transmits these to the central office (CO).
Step #3 – The central office routes the calls in the form of electrical signals through fiber optic cable. The fiber optic conduit then carries these signals in the form of light pulses to their final destination.
Step #4 – Your call is routed to a tandem office (a regional hub responsible for transmitting calls to distant central offices) or a central office (for local calls).
Step #5 – When your call reaches the right office, the signal is converted back to an electrical signal and is then routed to a terminal.
Step #6 – The terminal routes the call to the appropriate telephone number. Upon receiving the call, the telephone set converts the electrical signals back to sound waves.
This may sound complicated, but the thing to remember is that it takes a few seconds for your call to reach its destination. This process is facilitated by using fiber optic cables and a global network of switching centers.

POTS diagram

Comments

Post a Comment

Popular posts from this blog

Introduction of Digital computer

-
Image
INTRODUCTION Digital computer concept:- 1. Digital computers are designed to store, process and communicate information in digital form. 2. Digital computer is any of a class of digital devices capable of solving problems by processing information in discrete form. 3. It is used for processing data represented by discrete, localized physica signals, as the presence or electic current. 4.The main three components of digital computer:- >input:- The user gives a set of input data through input devices. >Processing :- The input data is processed with the help of CPU by well defined and finite sequence of step. >Output : - Some data available from the processing step are output to the user. TYPE OF DIGITAL COMPUTER :- 1.Microcomputer/Desktop computer 2.Minicomputer 3.Mainframe computer 4.Supercomputers Microcomputer :- 1.Microcomputer is also called a personal computer or desktop computer. 2.It includes a microprocessor, memory, and
Read more

INTRODUCTION OF DBMS

-
What is Database :- The database is a collection of inter-related data which is used to retrieve, insert and delete the data efficiently. It is also used to organize the data in the form of a table, schema, views, and reports, etc. For example: The college Database organizes the data about the admin, staff, students and faculty etc. Using the database, you can easily retrieve, insert, and delete the information. DBMS (Database Management System):- Database management system is a software which is used to manage the database. For example: MySQL, Oracle, etc are a very popular commercial database which is used in different applications.DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more.It provides protection and security to the database. In the case of multiple users, it also maintains data consistency. DBMS allows users the following tasks:- Data Definition: I
Read more

Introduction to cache memory

-
Image
Cache Memory in Computer Organization Cache Memory  is a special very high-speed memory. It is used to speed up and synchronizing with high-speed CPU. Cache memory is costlier than main memory or disk memory but economical than CPU registers. Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU. It holds frequently requested data and instructions so that they are immediately available to the CPU when needed. Cache memory is used to reduce the average time to access data from the Main memory. The cache is a smaller and faster memory which stores copies of the data from frequently used main memory locations. There are various different independent caches in a CPU, which stored instruction and data. Levels of memory: Level 1 or Register – It is a type of memory in which data is stored and accepted that are immediately stored in CPU. Most commonly used register is accumulator, Program counter, address register etc. Level 2 or Cac
Read more