Second Chapter Lesson-1: Data communication, Data communication system and it’s efficiency.

At the end of this lesson-

  • 1. You will be able to explain the concept of data communication.
  • 2. You will be able to describe the elements of data communication system.
  • 3. You will be able to explain the data communication speed.


Data communication: Data communications refers to the transmission of the digital data between two or more nodes in a network. Emails, SMS, Phone calls, Chatting etc. are examples of data communication.

For data communication between digital devices softwares are required. These softwares are called communication software.

Data communication system: Communication system is a collection of communication devices and networks to transmit data/information among different nodes.

There are several types of communication systems. Such as:

  • Telephone communication system.
  • Mobile phone communication system.
  • Computer based communication system.
  • Internet based communication system.

Elements of Data Communication: Data communication system has five basic components.

  1. Source
  2. Transmitter/Sender
  3. Medium
  4. Receiver
  5. Destination

Source: The device from which data is sent. Example- Computer, Telephone.

Transmitter/Sender: The device that make data for transferable and send to the receiver through media. Example- Modem.

Encode: Conversion of human language to machine language.

Medium: That connects source and destination and through which data is transmitted. It may be wired and wireless.

Receiver: The device that receive data from communication medium and convert it for destination.  Example- Modem.

Decode: Conversion of machine language to human language.

Destination: The device where data is sent or target device. Example – computer, telephone.


Efficiency of a data communication system:

Efficiency of a data communication system mainly depends on the following data transmission characteristics.

  1. Data Transmission Speed
  2. Data Transmission Mode
  3. Data Transmission Method
  4. Data Transmission Medium


Data Transmission Speed: The data transfer rate of a communication system is called bandwidth or band speed or data transmission speed. or The amount of data (bit) that is transmitted per second. It is measured in bit per second or baud unit.

Bit means binary 0 or 1. that is noted by b.

1 byte= 8 bit

1 kilobyte= 1024 Byte

1 Megabyte = 1024 Kilobyte

1 Gigabyte = 1024 Megabyte

1 Terabyte = 1024 Gigabyte

There are three types of bandwidth.

Narrow band(45 – 300 bps): Data is transferred in a speed from 45 to 300bps. It is used in telegraph communication system.

Voice band(1200 – 9600 bps): Data is transferred in a speed from 1200 to 9600bps. It is used in telephone system and also used in computer or peripheral devices.

Brod band(1Mbps +): Data is transferred in a speed from 1 Mbps to very high speed. It is used in data transmission through optical fiber cable and microwave.

Lesson Evaluation-

Knowledge Based Questions:

  • a. What is data communication?
  • a. What is data communication system?
  • a. What is channel?
  • a. What is bandwidth/data transmission speed?
  • a. What is narrow band?
  • a. What is voice band?
  • a. What is brod band?

Comprehension Based Questions:

  • b. What do you understand by bandwidth 58kbps?
  • b. Explain 9600bps.
  • b. Which band is indicated by 1.4kbps? explain.
  • b. Explain the bandwidth of mobile phone.
  • b. Explain the bandwidth of telegraph.

Creative Questions:

Multiple Choice Questions:


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