Communication means the exchange of information or messages. When we talk with each other, we are exchanging information. Data communication can be defined as: “By using the transmission media, data or information is transmitted from one location to another is called data communication”. For data communication, computers, telephones, and wireless devices that are linked in a network are used. Physical transfer of data over a point to point (communication connection between two nodes or end points) or point to multi-point (communication which is accomplished via distinct type of one to many connection) channel is called data transmission.
Components or Elements of a Data Communication:
There are five elements of a data communication system:-
- Medium (Communication Channel)
- Encoder & Decoder
The message is the information or data that is communicated. It may consist of text, numbers, images, sound, video etc.
The computer or device that sends the data or messages is called sender. In data communication system, computer is usually used as a transmitter. It is also called sender. A sender may be computer, workstation, telephone, video camera etc.
The device that receives the data or messages is called receiver. Receiver is also known as sink. The receiver can be a computer, workstation, printer or a fax machine.
Medium (Communication Channel):
The path through which data is sent or transmitted from one location to another is called communication channel. If the receiver and the sender are within a building, a wire may be the communication channel. If they are located at different locations, the channel may be the telephone lines, fibre optics, satellite or microwaves.
The computer works with digital signals. The communication channels usually use analog signals. Therefore, to send data through a communication channel, the digital signals are encoded (or converted) into analog signals or into a form which can be transmitted through transmission medium. This is called encoding. The device that carries out this function is called encoder.
The computer works with digital signals. The communication channels usually use analog signals. Therefore, to receive data from a communication channel, the coded analog signals or any other encoded form are converted back to digital signals. This is called decoding. The device that carries out this function is called decoder.
Types of Data used in a Data Communication System:
Data used in communication system may be consisting of text, numbers, images, audio and video. The different types of data are as under:-
Text and Numeric Data:
Text data consists of words, sentences and paragraphs. The text is normally stored as ASCII code format. The numeric data can be represented in different number systems, e.g., decimal, hexadecimal, octal and binary number system.
Audio & Video Data:
Audio data are continuous wave forms and not discrete. Audio data comprises sound. Sound may be any music, speech or any other sound stored electronically. Video data comprises motion pictures that create actions and movements. It can be a set of motioned pictures. It can be produced by a video camera.
Images may be charts, graphs, pictures, sketches and freehand drawings. Image data is also represented by bit patterns.