Modes of Transmission Long Answer Type Questions (8 Marks)

Question 1.
What are the different transmission modes? (UP 2004, 16)
Or
What is simplex and duplex modes of transmission? (UP 2006, 07)
Or
Explain ‘Simplex’ and ‘Duplex’ system. Why is the duplex system more popular? (UP 2011, 12)
Or
Describe in brief duplex. (UP 2016)
Or
What is Simplex Communication? (UP 2018)
Answer:
Data Transmission Modes: The term ‘transmission mode’ is used to define the direction of signal flow between two linked devices.
There are three ways or modes for transmitting data from one point to another. These are:

1. Simplex
2. Half-duplex
3. Full-duplex.

1. Simplex: If the transmission is simplex, communication can take place in only one direction. Devices connected to such a circuit is either a send-only or a receive-only device. For example, broadcasting of signals to the television. In this case, TV can receive signals only, it cannot send back signals to satellite or any other device.

In data processing applications, communication in both directions is required. Even for a ‘one-way’ flow of information from a terminal to a computer, acknowledgement from the terminal to the computer is required. Thus, simplex circuits are seldom used in data communication.

2. Half-duplex: Signals can be transmitted from both sides but hot at a time. In half-duplex transmission, you can transmit signals in both directions, but not simultaneously. If the communication line is busy, then the message will be in a wait state. The buffer transmits that signal first, which is accepted first. Example of this kind of transmission is E-mail. When we send a message from our inbox to an E-mail address then the following message appears:
Your message has been sent to the following recipient: chan- dress-5 @ Indiatimes. com.
This is an acknowledgement, confirming that the message has reached to its recipient.

3. Full-duplex: Some applications require simultaneous transmission in both directions. In such cases, a full-duplex system is used that allows information to flow simultaneously in both directions on the transmission path. Examples of these transmission techniques are telephone system and signal transmission between different computer hardware devices.
One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time.

Question 2.
Write about different communication channels?
Answer:
The communication data transfer rate is measured in bits per second (bps) or band, depending on their transmission speed. Communication channels (paths) are grouped into three basic categories: narrowband, voiceband and broadband.
Narrowband: When the data transfer rate is between 45 to 300 bps then this is called Narrowband transmission. They are used mainly for telegraph lines and low-speed terminals.

Voiceband: Voiceband channels handle moderate data volumes and can transmit data at speed up to 9600 bps. They are so-called because their major application is for ordinary telephone voice communication. Most remote terminals are connected to computers through voiceband channels.

Broadband: Broadband or wideband channels are used when a large volume of data is to be transmitted at high speed. These systems provide data transmission rates of 1 million (106) bps or more. Nowadays, broadband communication is gaining popularity. This is basically used in mobile devices such as cellular phone, laptop, notebook etc.

Question 3.
Explain the following: (UP 2004)
(a) Analogue transmission
(b) Digital transmission.
Answer:
Data is propagated from one point to another by means of electrical signals which can be of two forms:

1. Analogue signals, and
2. Digital signals.

In the analog signal, the transmitted power varies over a communication range as in sound, light and radio waves.

Digital signals are coded representation of information. Keyboard characters, for example, are usually encoded in binary digit code.
The digital signal is a sequence of voltage pulses represented in binary form.
Computer-generated data is digital whereas telephone lines used for data communication in computer networks are usually meant for carrying analogue signals. When digital data are to be sent over an analogue facility, the digital signals must be connected to analogue form. This is usually done by using a device called modem that is capable of connecting a digital signal to analogue and vice-versa.

Question 4.
What is meant by wired and wireless communication system? List their advantages and disadvantages. (U. P. 2007)
Answer:
The medium is the matter or substance that carries the voice or data transmission. It can be copper, glass, or wave. A circuit is nothing more than the path over which data moves. Communication media is of two types:
(A) Wired Media: In this type of media, wires are used. It is further classified into three categories:

1. Twisted Pair Cable: Twisted pair of wires is the main media used in local telephone communication and short distance (less than 1 km) digital data transmission. Pairs of wire are twisted together to reduce interference by adjacent wires. Wires are usually made of copper. This medium is inexpensive.
The main advantages of twisted pair cable are its simplicity and ease of installation. It is physically flexible, has a low weight and can be easily connected.

The twisted pair is used for audio telephone communication with speech signal bandwidth of 4 kHz. However, it has much higher bandwidth of about 50 kHz. The speed of digital signal transmission using telephone lines is 1200 bps (bits per second) (Also commonly quoted as 1200 bands).

Twisted pairs are used to connect terminals to the main computer. In this case, the speed of transmission is up to 9.6 kbps, if the length is less than 100 metres. Noise pick up by twisted wire which results in high error rates when the line length is more than 100 metres. This limits the use of twisted pair.

2. Coaxial Cable: Coaxial cables are groups of specially wrapped and insulated wire lines that are able to transmit data at high rates. They consist of a central copper wire surrounded by a PVC insulation over which a sleeve of copper mesh is placed. The metal sleeve is again shielded by an outer shield of thick PVC material. The signal is transmitted by the inner copper wire and is electrically shielded by the outer metal sleeve.

Coaxial cables offer much higher bandwidth and are capable of transmitting digital signals at a very high rate of 10 Mbps. They are extensively used in long-distance telephone lines and cable TVs. They can handle 15,000 telephone calls simultaneously. Coaxial cables have much higher noise immunity and can offer data transmission without distortion or loss of signal.

3. Fibre Optic Cable: Physically, an optical fibre consists of a glass core, a plastic or glass cladding and a protective coating. The ore diameter is between 8 and 200 micrometres. Optical fibres have several advantages. They are:

• Very high bandwidth.
• Protection against electromagnetic interference.
• More secure as they cannot be tapped easily.
• Lightweight and no corrosion.

The major disadvantages of fibre optic cables are:

• It is difficult to align and join two fibres in the field without using special equipment.
• They are fragile and cannot have sharp bends.

In fibre optic communications, electrical signals are transformed into light pulses by a modulator, transmitted over the fibre as light waves, detected and converted back to electrical signals by photoelectric diodes.

(B) Wireless Media: In this type of media, wires are not used, hence, there is no physical connection. It is further classified into two categories:
1. Microwave: Parabolic antennas are mounted on towers to send beams. It is cheaper than digging trenches for laying cables, and maintaining repeaters of cables if cables get broken by a variety of causes. Transmitter and receiver must be in the line of sight—30 miles apart because of earth curvature, possible interference from the environment, lack of security, high initial equipment cost. Relatively high-speed data rates up to 250 Mbps.
Usage: Voice Communication (Cellular Services).

2. Satellite: There is a need of 12 to 24 transponders per satellite. These transponders receive, amplify, change frequency and transmit. Geosynchronous orbit (22,300 miles) Low security-anyone with satellite dish and right frequency can tune in. Ease of adding stations. Data rates up to 50 Mbps. Microwave signal at 6 GHz is beamed to it from a transmitter on the earth. It is amplified and retransmitted to the earth at 4 GHz by a system called transponder mounted on the satellite to avoid interference.

Question 5.
What is meant by Protocol? What protocols are used on the internet? Explain. (UP 2008)
Or
What is the Protocol? Why is it needed in networks? Explain. (UP 2011)
Or
Write in brief Protocol. (UP 2017)
Answer:
Protocol: Protocol is a software, i.e., set of rules which are used to establish communication between several computers. It defines the exact order in which two machines exchange data with one another. Protocols are technical customs or guidelines that govern the exchange of signal transmission and reception between equipment. Each protocol specifies the exact order in which signals will be transferred. Both Hardware and software are designed to handle specific protocols.
Functions of Protocol: There are the following functions of protocol:

• How to begin and terminate a session between two computers?
• How the messages in a session are to be framed?
• How errors in the transmission of messages are to be detected?
• How messages are to be retransmitted when errors are detected?
• How to find out which message block was sent by which terminal computer and to whom?
• How the dialogue on the communication line proceeds?

Examples:

1. TCP/IP (Transmission Control Protocol/Internet Protocol): TCP breaks up the data to be sent into packets. It guarantees that any data sent to the destination computer reaches it. IP is a set of conventions used to send packets from one host to another. It is responsible for routing the packets to a desired destination IP address.
2. X.12: This protocol is used to establish a connection between companies to exchange important papers.
3. X. 25: This protocol establishes the interface for common data network.
4. HTTP: HyperText Transfer Protocol works on the internet to send or receive files from different locations.

Modes of Transmission Short Answer Type Questions (4 Marks)

Question 1.
What do you mean by bandwidth? (UP 2008, 18)
Answer:
A term used to describe the data-handling capacity of a communication system is bandwidth. Bandwidth is the range of frequencies that is available for the transmission of data. A narrow range of frequencies in a communication system is analogous to a narrow road, i.e., its data transfer rate is limited, just like the flow of traffic on a narrow road. Wider bandwidth permits more data transfer through the communication channel at the same time.

Question 2.
What is data transmission speed? (UP 2016, 19)
Answer:
In computer communication, the amount of data transferred from one place to another in one second is known as data transmission speed. It is measured in bps (bits per second) kbps (kilobytes per second), Mbps, etc. There are three communication channels on the basis of data transmission speed:

• Narrowband transmission – 45 to 300 bps
• Voice band transmission – up to 9600 bps
• Broadband transmission – 106 bps or more

Question 3.
What is a MODEM? (UP 2008, 12, 15, 18)
Answer:
A modem is a device which is used to connect a computer to a telephone line for the purpose of transmission. It is because of a modem, your PC can be connected to the internet through a telephone line. The computer is a digital device and it works on digital signals whereas the telephone is an analogue device and works on analogue signals. At both the ends, computers are connected to telephone lines through modem because it is modem which converts digital signals to analogue and again back to digital signals at receiving end. The process of converting digital signals to analogue signals is called Modulation and the process of converting analogue signals to digital is known as Demodulation,
(Modem = Modulation + De = Modulation)

The speed of transmission is measured in bps. Modems usually operate at speeds ranging from 2,400 to 28,800 bits per second over standard telephone lines, and at faster rates over leased lines. A suitable communication program is needed to operate the modem.

Question 4.
Write the type of connections. (UP 2017)
Answer:
There are three types of connections:
1. Dial-up connections: This is a kind of connection which is available through telephone lines. Through this, we can connect to the local exchange and for this, we have to dial a number. After the establishment of the connection, we can transfer information. This service is also known as switching service and its bandwidth is less than 400 Hz.

2. Leased-Lines: This service provides user 24-hour connection. This connection is also available through telephone lines but through switches. This is uninterrupted service.

3. Integrated Service Digital Network (ISDN): This service is totally dedicated to the computer because separate lines are used for the purpose of transmission. Mostly co-axial cable is used for this. In this digital transmission, media is used and one can send voice, data etc. through this connection.

Modes of Transmission Very Short Answer Type Questions (2 Marks)

Question 1.
What is the full form of MODEM? (UP 2015)
Answer:
Modulation and Demodulation.

Question 2.
Which type of signals travels over telephone lines?
Answer:
Analogue signals.

Question 3.
Which transmission channel has the highest bandwidth?
Answer:
Broadband channel.

Question 4.
What is the data transfer rate of Narrowband Channel?
Answer:
300 to 9600 bps.

Question 5.
In which mode, communication is unidirectional?
Answer:
Simplex Mode.

Question 6.
In which type of transmission, collection of 8 wires is needed to transmit 8 bits? (UP 2008, 11)
Answer:
Parallel transmission.

Modes of Transmission Objective Type Questions (1 Mark)

There are four alternative answers for each part of the questions. Select the correct one and write in your answer book:

Question 1.
E-mail is an example of:
(a) Network
(b) Simplex
(c) Duplex
(d) Half-duplex.
Answer:
(d) Half-duplex.

Question 2.
Converting digital signal into an analog signal is known as:
(a) Modem
(b) Modulation
(c) De-modulation
(d) Transmission.
Answer:
(b) Modulation

Question 3.
The process of converting an analog signal into digital is known as:
(a) Modulation
(b) De-modulation
(c) Analog Transmission
(d) Digital Transmission.
Answer:
(b) De-modulation

Question 4.
The data handling capacity of a communication system is known as:
(a) Bandwidth
(b) Narrow Band
(c) Voice Band
(d) BroadBand.
Answer:
(a) Bandwidth

Question 5.
T.V. is an example of:
(a) Simplex Mode of transmission
(b) Half-duplex Mode of transmission
(c) Full-duplex Mode
(d) None of these.
Answer:
(d) None of these.

Question 6.
Which one of the following is not a protocol?
(a) TCP/IP
(b) ISP
(c) HTTP
(d) X.25.
Answer:
(b) ISP

Question 7.
Telephone lines carry which type of signals:
(a) Analog
(b) Digital
(c) Hybrid
(d) None of these.
Answer:
(a) Analog

Question 8.
Bits are transferred sequentially one by one in:
(a) Parallel Transmission
(b) Analog Transmission
(c) Serial Transmission
(d) None of these.
Answer:
(c) Serial Transmission

Question 9.
Which connection is available through telephone liens?
(a) Dial-up
(b) Leased-lines
(c) ISDN
(d) Both (a) and (b).
Answer:
(d) Both (a) and (b).

UP Board Solutions for Class 10 Computer Science