Data Communication with standard telephones lines By Muhammad Ahtsham

1

BS(ELECTRICAL)TOPIC: DATA COMMUNICATION BY STANDAERD TELEPHONES LINES

Muhammad Ahtsham

Data Communication with standard telephones lines By Muhammad Ahtsham

2

Data communications

It is an application of telecommunications technology for the purpose of transmitting data.

It transmit data especially to, from , or between computers.

It refers to the moving or transferring of data between two electronic devices.

Brief History of Data Communication

1838: Samuel Morse & Alfred Veil Invent Morse Code Telegraph System

1876: Alexander Graham Bell invented Telephone

1910: Howard Krum developed Start/Stop Synchronization.

1930: Development of ASCII transmission Code 1945: Allied Governments develop the First Large Computer 1950: IBM releases its first computer IBM 710 1960: IBM releases the First Commercial Computer IBM 360 Than from IC and microchips till SS7, Data communication is so

easy that today data is transferred in fraction of seconds.

Data Communication with standard telephones lines By Muhammad Ahtsham

4

At least Two Devices ready to communicate A Transmission Medium A set of Rules & Procedure for proper communication

(Protocol) Standard Data Representation Transmission of bits either Serial or Parallel Bit synchronization using Start/stop bits in case of Asynchronous Transmission In Synchronous Transmission the agreed pattern of Flag Signal encoding rules viz. NRZ or RZ Other higher layer protocol

Requirements of Data Communications

Data Communication with standard telephones lines By Muhammad Ahtsham

5

Communications Channels

A communications channel is a pathway over which information can be conveyed.

It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence.

Data Communication with standard telephones lines By Muhammad Ahtsham

6

Types of Communication

Microwave Communications:• Line-of-sight devices which must be placed in relatively

high locations.• Information is converted to a microwave signal, sent

through the air to a receiver, and recovered.

Data Communication with standard telephones lines By Muhammad Ahtsham

7

Satellite transmission:• Communications satellites are relay stations that

receive signals from one earth station and rebroadcast them to another.

• They use microwave signals.

Data Communication with standard telephones lines By Muhammad Ahtsham

8

Telephone circuits are often used to transfer data.

Telephone networks use circuit switching. The telephone network had its beginnings in the late 1800s. The entire network, which is referred to as the plain old telephone system (POTS), was originally an analog system using analog signals to transmit voice.

Networks commonly use dedicated media to transmit data. However, the public telephone system can also be used for data communications.

Standard phone lines transmit data much more slowly than network media.

Data Communications over Standard Telephone Lines

Data Communication with standard telephones lines By Muhammad Ahtsham

9

Devices such as modems make phone lines practical for data transmission over long distances.

Most telephone lines are analog, not digital.

Modem converts it from analog format to digital format.

Data Communications over Standard Telephone Lines - Modems

Data Communication with standard telephones lines By Muhammad Ahtsham

10

As PCs transmit and receive data in digital format, a device called a modem is needed to convert digital data to analog format for transmission over phone lines (MOdulation).

When receiving data from another computer, the modem converts it from analog format to digital format (DEModulation).

Data Communication with standard telephones lines By Muhammad Ahtsham

11

`

The analog signal(audible)

is sent throughtelephone lines.

MODEM MODEM 011010001011010001

Digital signalDigital signal

This modem convertsdigital to analog.

This modem convertsanalog to digital.

Data Communication with standard telephones lines By Muhammad Ahtsham

12

When choosing a modem, consider the following factors:

Transmission speed: The speed at which the modem sends data - which is measured in bits per second.

Data compression: The technology the modem uses to shrink data so it can be transmitted faster.

Error correction: The method the modem uses to ensure data is sent and received without errors.

Internal versus external: It describes whether or not the modem fits inside the PC case.

Data Communications over Standard Telephone Lines - Choosing a Modem

Data Communication with standard telephones lines By Muhammad Ahtsham

13

Telephone companies are now installing digital telephone lines which are dedicated to transmitting data in digital format.

Digital phone lines transmit data at much higher speeds than standard analog phone lines.

Often, data travels across analog lines and digital lines. In such cases, data may need to be converted from one format to another multiple times before reaching its destination.

Using Digital Telephone Lines

Data Communication with standard telephones lines By Muhammad Ahtsham

14

Data Communication with standard telephones lines By Muhammad Ahtsham

15

Follow Me on Facebook: https://www.facebook.com/masoompunchii856Follow Me on Twitter: @GBA856Follow me on Linkedin: http://www.linkedin.com/profile/view?id=302219822&authType=name&authToken=Mgam&trk=api*a199685*s207772*Email Id: Mahtshamm856@gmail.com

Contact Details

Data Communication with standard telephones lines By Muhammad Ahtsham

16