CBSE Class 9 Foundation of Information Technology NCERT Solutions Chapter 4: Communication Technology

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 9 PDF

This chapter provides essential NCERT Solutions for Class 9 Foundation of Information Technology, focusing on Chapter 4: Communication Technology. It delves into the fundamental concepts of how information is transmitted and shared. The solutions explain what a computer network is, the importance of communication channels, and the different types of networks like LAN, MAN, and WAN. It also touches upon the physical aspects of network connections, such as twisted pair and fiber optic cables, and the principles behind the internet as a 'network of networks'. These solutions are designed to help students understand the core principles of communication technology, crucial for their IT studies and exam preparation.

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Board	CBSE
Class	Class 9
Subject	Foundation of Information Technology
Session	2026
Language	English
Type	NCERT Solutions
Chapter	4. Communication Technology

Chapter summary

Chapter 4 of the Class 9 Foundation of Information Technology syllabus focuses on Communication Technology. The NCERT Solutions provided cover key concepts including the definition of a computer network, the necessity of meaningful information exchange for communication, and examples of communication technologies. It details the essential components of a computer network, the role of communication channels, and categorizes networks into LAN, MAN, and WAN. The solutions also explain the types of transmission media (guided vs. unguided) and specific cable types like twisted pair and fiber optic, along with the reasons for twisting wires.

Learning outcomes

Understand the definition and purpose of a computer network.
Identify examples of communication technologies.
Explain the components required for establishing a computer network.
Differentiate between various types of computer networks (LAN, MAN, WAN).
Recognize the function and types of communication channels.
Explain the difference between guided and unguided transmission media.

Topics covered

Paper topics

Computer Network Definition
Communication Definition
Communication Technology Examples
Components of a Computer Network
Communication Channel Importance
Types of Computer Networks (LAN, MAN, WAN)
LAN Cable Types
Internet as Network of Networks
Guided vs. Unguided Transmission
Twisted Pair Cable Function

Important topics

Definition and components of a computer network
Types of computer networks (LAN, MAN, WAN)
Role and types of communication channels
Guided vs. Unguided transmission media

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Questions and Solutions

Question 1.

Name the term defined by the given statement: "A group of computers connected to each other by a link."

Solution: The term defined by the statement "A group of computers connected to each other by a link" is a Computer Network. A computer network allows multiple devices to communicate and share resources.

Question 2.

Two people, one knowing only English and the other knowing only Chinese, are talking to each other. Can we call it a communication?

Solution: No, this cannot be called effective communication. Communication requires a meaningful exchange of information where both parties can understand each other. Since there is a language barrier, the exchange of information is not meaningful, and therefore, it is not considered communication in the technical sense.

Question 3.

Give a few examples of communication technology.

Solution: Communication technology encompasses various tools and systems used for transmitting information. Some common examples include:

Telephones
Mobile phones
Fax machines
The Internet
Radio and Television broadcasting

Question 4.

Write down the components of a computer network established between the two offices of a company located across different cities.

Solution: Establishing a computer network between two offices in different cities involves several key components to ensure data can be sent and received reliably. These components are:

Sender: The device or system that originates the data to be transmitted. This could be a computer in one office.
Data communication device at sender's end: This is a device like a modem or router that prepares the data for transmission over the communication channel.
Communication Channel: This is the medium through which the data travels from the sender to the receiver. In this case, it would likely be telephone lines or dedicated leased lines connecting the cities.
Data communication device at receiver's end: Similar to the sender's end, this device (e.g., a modem or router) receives the data from the channel and converts it into a format the receiver can understand.
Receiver: The device or system that ultimately receives the data. This would be a computer in the other office.

Question 5.

What is the importance of a communication channel?

Solution: The communication channel is a critical component of any network because it serves as the pathway for data transmission. Its importance lies in its responsibility for carrying data, typically in the form of electrical or electromagnetic signals, from the sender's device to the receiver's device. The efficiency, speed, and reliability of data transfer are heavily dependent on the type and quality of the communication channel used.

Question 6.

List down the types of computer networks.

Solution: Computer networks are primarily classified based on their geographical coverage. The three main types are:

Local Area Network (LAN): Covers a small geographical area, such as an office building, home, or campus.
Metropolitan Area Network (MAN): Spans a larger area than a LAN, typically a city or a large campus.
Wide Area Network (WAN): Covers a broad geographical area, potentially spanning countries or even the entire globe, like the Internet.

Question 7.

Which cable networks are used for LAN connections?

Solution: For establishing Local Area Network (LAN) connections, two primary types of cable networks are commonly used:

Twisted pair cables: These are the most common type, consisting of pairs of insulated copper wires twisted together to reduce electromagnetic interference.
Fibre optic cables: These cables transmit data using light pulses through thin strands of glass or plastic, offering higher bandwidth and longer transmission distances than twisted pair cables.

Question 8.

Why is the Internet called a network of networks?

Solution: The Internet is referred to as a "network of networks" because it is not a single, unified network. Instead, it is a vast, interconnected system comprising millions of smaller private, public, academic, business, and government networks. These diverse networks, ranging from small local networks to large international ones, are linked together using standardized communication protocols, forming a global network.

Question 9.

Give one basic difference between guided and unguided transmission channels.

Solution: The fundamental difference between guided and unguided transmission channels lies in how data signals are directed:

Guided Transmission Channels: These media use physical pathways, such as cables (like twisted pair, coaxial, or fiber optic cables), to guide the data signals from the sender to the receiver. The signals are confined within the physical medium.
Unguided Transmission Channels: These media do not use physical cables. Instead, data signals (like radio waves, microwaves, or infrared signals) travel through the air or space, broadcasting in different directions or being focused in a beam.

Question 10.

Why are wires in a twisted pair cable twisted around each other?

Solution: The wires in a twisted pair cable are twisted around each other primarily to reduce electromagnetic interference (EMI) and crosstalk. When two wires carrying electrical signals are twisted, the electromagnetic fields generated by each wire tend to cancel each other out. This twisting helps to minimize noise pickup from external sources and reduces the signal interference between adjacent pairs of wires, leading to more reliable data transmission.

Common mistakes

Confusing communication with mere connection without meaningful data exchange.
Not listing all essential components of a computer network.
Inability to distinguish between different types of network classifications (e.g., by area).
Not understanding the role of the communication channel in data transmission.

Revision tips

Review the definitions of key terms like 'computer network' and 'communication channel'.
Memorize the different types of computer networks (LAN, MAN, WAN) and their characteristics.
Understand the components needed to set up a network between two locations.
Pay attention to the examples provided for communication technologies and network types.

Practice MCQs

Q1. What is the primary definition of a computer network?

Q2. Which of the following is NOT considered a communication technology?

Q3. What is the main role of a communication channel in a network?

Q4. Which type of network typically covers the largest geographical area?

Q5. Why are wires twisted in a twisted pair cable?

Frequently asked questions

What is a computer network according to Chapter 4?

A computer network is defined as a group of computers that are interconnected with each other through a link, enabling them to share information and resources.

What are the main types of computer networks discussed?

The chapter discusses three main types of computer networks based on geographical area: Local Area Network (LAN), Metropolitan Area Network (MAN), and Wide Area Network (WAN).

Why is the Internet called a 'network of networks'?

The Internet is called a 'network of networks' because it connects numerous large and diverse networks together, forming a single, massive global network.

What is the purpose of a communication channel?

A communication channel is essential for carrying data in the form of signals from the sender's device to the receiver's device.

What is the difference between guided and unguided transmission channels?

Guided transmission uses physical cables like twisted pair or fiber optic to direct signals, while unguided transmission uses signals that travel through the air, like radio waves or microwaves.

How do these NCERT Solutions help in exam preparation?

These solutions provide clear, rewritten answers to all questions, explaining concepts step-by-step, which aids in understanding and revising the chapter for exams.

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