Fbise Notes-Computer

Long Question Answers Chapter No.4

i. Describe the components of communication system with the help of diagram.

Ans: Components of a Communication System:

Communication system consists of the following five basic components;

i. Sender

ii. Receiver

iii. Message

iv. Transmission Medium

v. Protocol

Sender:

It is the device which sends the message. In other words, it is the source of message that can be a computer, telephone or any other device.

Receiver:

It is the device which receives the message. In other words, it is the destination of message that can be a computer, radio , telephone or any other device.

Message:

It is the data to be transmitted. It can be text, graphics, image, sound or video.

Transmission Medium:

It is the physical pathway over which the message is send from sender to receiver. Some examples of transmission media are coaxial cable, fiber optic cable and microwaves etc.

Protocol:

It is the set of rules between the two communicating devices that governs the process of data communication. Without a protocol, two devices may be connected but they cannot communicate with each other.

➤➤➤➤➤➤➤➤➤➤➤➤

ii. Explain asynchronous and synchronous transmission modes with examples.

Ans: Asynchronous Transmission:

The transmission mode in which time interval between each character is not the
same is known as asynchronous transmission. Some of the features of this transmission are;

I. Each character is transmitted with additional control information.Control information consists of additional start and stop bits. These bits indicate
the start and stop of transmission.

Start bit is 0 and stop is 1.

II. The characters are transmitted at uniform time intervals.

III. This transmission is slow because additional bits transmitted with each character.

synchronous Transmission:

The transmission mode in which time interval between the characters is always the same, is known as synchronous transmission. Some of the features of this transmission are;

I. There is no control information added with the characters.

II. 0s and 1s bits are transmitted as one long stream of bits. The receiver count these bits.

III. This transmission is faster than asynchronous because it does not require extra start and stop bits.

➤➤➤➤➤➤➤➤➤➤➤➤

iii. Describe the following guided media.

Ans: Twisted Pair Cable:

It is the most commonly used cable for data communication. It consists of pairs of copper wires twisted around one another. The purpose of twisting is to reduce cross talk and electromagnetic interference. Transmission speed of twisted pair cable ranges from 2 million bits per second to 10 billion bits per second.

Example: Telephone cable consists of two twisted insulated wires, computer network cable consists of 4 pairs of twisted cables.

Co-axial Cable:

It is used for local area networks and cable television systems. It consists of copper wire surrounded by insulating layer. The insulating layer itself is surrounded by conductive layer. Insulation reduces interference and distortion. Transmission speed ranges from 200 million bits per second to more than 500 million bits per second.

Fiber Optic Cable:

Fiber optic cable consists of smooth hair-thin strands of transparent material. In fiber optic communication, the transmitter has a converter that converts electrical signals into light waves. These light waves are transmitted over the fiber optic cable. Another converter is placed at the receiving end that converts the light waves back to electrical signals.

A single fiber optic cable can carry up to 50,000 communication lines. It provides high quality transmission at extremely fast speed. It can transmit trillions of bits per second. It is not affected by electromagnetic fields and can transmit both analog and digital signals. It is used for data transmission over long distance.

➤➤➤➤➤➤➤➤➤➤➤➤

iv. Describe any three types of unguided media.

Ans: Unguided Media:

Unguided media signals travel through open space and nothing

guides them along any specific path. They do not use cables for data

transmission.

Types of Unguided Media:

Unguided media can be classified into radio waves, microwave,

infra-red and satellite communication .

Radio Waves:

They are electromagnetic waves that are propagated by antennas.

Radio transmission consists of a transmitter and a receiver. A transmitter

transmits a radio signal to a receiver which receives it. Radio waves are used

to transmit music, conversation, pictures and data. Data can be transmitted

over a long distance using radio waves. These waves are invisible and

undetectable to human beings.

The following are some applications of radio waves:

i. Radio and television broadcast.

ii. Cell Phone communication.

iii. Radio controlled toys.

iv. Satellite communication.

v. Wireless networks and wireless Internet.

Microwave:

Microwave signals travel through open space like radio waves. They

provide much faster transmission rate than telephone lines or co-axial cables.

They are installed on high buildings or high towers. They are used for satellite

communication and other long distance wireless communication.

Infra-Red:

These waves are light energy that we cannot see. It travels through

space at the speed of light. It is used for short distance communication. They

are usually used in remote controls for television, DVD players and other

similar devices. They are also used in industrial, scientific and medical

appliances.

Bluetooth:

Bluetooth is a wireless communication technology that uses radio

waves to connect portable electronic devices over short distance. These

devices include mobile phone, laptop, mouse , keyboard, wireless speaker,

wireless headset and pc etc. Bluetooth technology can transmit text, image,

voice and video.

Satellite:

A satellite is an object that is placed in an orbit around the earth and

revolves around it with speed that is slightly faster than Earth’s average orbital

speed for communication. It is a wireless reciver and transmitter used for

transmitting data over long distance at high speed.

Ground stations beam signals through antennas to satellite. Satellite amplify

and retransmit the signals to another ground station which can be located

many thousands of miles away.

➤➤➤➤➤➤➤➤➤➤➤➤

v. Describe the functions of the following communication devices.

Ans: Router:

Router is the communication device that is used when two networks have to be connected for communication. They send information from one network to another by selecting the best pathway available.

Types of Routers:

There are two types of routers

a. Wired Router.

b. Wireless Router.

Network Interface Card(NIC):

Network interface card or simply network card is used to connect computers together to create computer network. It makes communication between computers possible it is installed on the motherboard, in modern computers it is integrated on the motherboard.

Types of NIC card:

a. Wired network card.

b. Wireless network card.

Switch/Access Point:

A switch or access point is used for connecting computers together in local area network. Switch is used in wired networks whereas access point is used in wireless networks. A switch/access point receives information from a computer in the network, inspects it and then transmits it to the destination computer.

➤➤➤➤➤➤➤➤➤➤➤➤