Q.The device which works of both modulation and demodulation is called
(A) Laser
(B) Radar
(C) Modem
(D) Fax
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Elements of a Communication System
A communication system, regardless of what it carries, is built from three essential blocks connected in a chain: a transmitter, a channel, and a receiver, with noise capable of entering and corrupting the signal at any point along the channel. The transmitter converts the message signal - first turned into electrical form by a transducer if it wasn't already electrical, as with sound - into a form suited to the channel. The channel, wired or wireless, carries the transmitted signal to the receiver, but may distort it or add noise along the way. The receiver then processes the received (possibly corrupted) signal …
A device that both encodes data onto a carrier and recovers data from a received carrier signal is named for exactly those two functions. …
The device that performs both modulation and demodulation is the modem → option (C).
The word MODEM is short for MOdulator–DEModulator. At the transmitting end it modulates a carrier with the digital data (modulation), and at the receiving end it recovers the data from the received modulate …
Showing the 12 most recent of 14 on this concept.
- CBSE 2026Set A1 markMCQQ.'World Wide Web' was invented by (A) Tim Berner-Lee (B) John Logie Baird (C) Alexander Bain (D) G. Marconi
›Reveal solutionSolution
The World Wide Web was invented by Tim Berners-Lee (1989).
The World Wide Web — the system of interlinked hypertext documents accessed over the Internet — was invented by the British scientist Tim Berners-Lee in 1989 while at CERN. John Logie Baird is associated with televis …
- CBSE 2026Set A1 markMCQQ.The example of a broadcast mode of communication is (A) radio (B) telephone (C) television (D) both (A) and (C)
›Reveal solutionSolution
Broadcast communication sends the same signal from one transmitter to many receivers — radio and television both do this.
Communication modes are classified as point-to-point (a dedicated link between two specific users, e.g. a telephone) or broadcast (one transmitter serves a large number of receivers simultaneously). Radio and television both transmit a single signal that anyone with a rece …
- CBSE 2026Set A1 markMCQQ.In a communication system, a repeater is (A) a receiver (B) a transmitter (C) a combination of a receiver and transmitter (D) none of these
›Reveal solutionSolution
A repeater is a receiver plus a transmitter: it picks up a weakened signal, amplifies and reconditions it, then retransmits it to extend range.
Signals attenuate over long distances. A repeater is placed along the path to overcome this: its receiver section picks up the incoming weak signal, the signal is amplified (and often reshaped), and its transmitter section sends it onward — usually at a different frequency to avoid interference. Thus a repeater i …
- CBSE 2025Set D1 markMCQQ.What type of wave is used in fibre optic communication? (A) Sound waves (B) Electromagnetic waves (C) Seismic waves (D) Mechanical waves
›Reveal solutionSolution
Fibre-optic communication carries signals as light pulses — electromagnetic waves — guided along the fibre by total internal reflection.
In optical-fibre communication, information is converted into pulses of light (usually infrared/visible) and sent down a thin glass or plastic fibre. Light is part of the electromagnetic spectrum, so the wave used is an electromagnetic wave.
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- CBSE 2024Set A1 markMCQQ.The device which works of both modulation and demodulation is called (A) Laser (B) Radar (C) Modem (D) Fax
›Reveal solutionSolution
The device that performs both modulation and demodulation is the modem → option (C).
The word MODEM is short for MOdulator–DEModulator. At the transmitting end it modulates a carrier with the digital data (modulation), and at the receiving end it recovers the data from the received modulate …
- CBSE 2023Set ANNUAL1 markQ.What is the function of a repeater used in communication system? OR How does the effective power radiated from a linear antenna depend on the wavelength of the signal to be transmitted?
›Reveal solutionSolution
A repeater is a receiver-cum-transmitter unit that boosts a weakened signal and relays it further, increasing the effective communication range.
A repeater is a combination of a receiver and a transmitter placed between the original transmitter and the final receiver. Its function is:
- It receives the signal from the transmitter (or from a previous repeater), which has become weak/attenuated due to propagation over distance.
- It amplifies this weak signal (and, in digital systems, regenerates/re-times it to remove accumulated noise and distortion).
- It re-transmits the amplified signal onward, either to the next repeater or to the final receiver. …
- CBSE 2023Set ANNUAL1 markMCQQ.In communication system, noise is most likely to affect the signal(a) at the transmitter(b) in the transmission medium(c) in the information source(d) at the destination
›Reveal solutionSolution
Noise is unwanted signal picked up along the path (channel) the signal travels through, so it is the transmission medium where it corrupts the signal most.
Noise refers to unwanted signals that tend to disturb the transmission and processing of a message signal. It typically enters the system from the environment surrounding the transmission channel — atmospheric disturbances, interference from other signals, thermal noise in the medium, etc. — while it travels from the transmitter to the receiver. The transmitter and receiver are engineered/shielded systems, and the information …
- CBSE 2023Set ANNUAL1 markMCQQ.Which of the following is not a transducer ?(a) Loudspeaker(b) Amplifier(c) Microphone(d) All of these
›Reveal solutionSolution
A transducer converts one FORM of energy into another; an amplifier only strengthens an electrical signal, staying within the same form of energy.
Why: A loudspeaker converts electrical energy into sound (mechanical) energy — a transducer. A microphone converts sound energy into electrical energy — also a transducer. An amplifier takes a weak electrical signal and produces a stronger electrical signal at its ou …
- CBSE 2020Set ANNUAL1 markQ.Draw block diagram of a communication system.
›Reveal solutionSolution
Figure — Left-to-right block diagram of a generalized communication system A communication system is represented as a chain of blocks: the message is picked up, converted to a signal, transmitted through a channel (which adds noise), then received and converted back for the user.
The basic block diagram of a communication system consists of the following blocks connected in sequence:
- Information Source — originates the message (e.g. a person speaking).
- Input Transducer — converts the message (sound, image, etc.) into an electrical signal.
- Transmitter — processes the electrical signal (amplification, modulation) so it can be transmitted efficiently over the channel; includes the Modulator.
- Channel — the physical medium (wire, free space, optical fibre) through which the signal travels from transmitter to receiver. Noise is shown as an external input added to the signal in the channel. …
- CBSE 2019Set HE2341 markQ.Give answer in one sentence: What is transducer?
›Reveal solutionSolution
A transducer converts one form of energy into another — e.g. sound into electrical signals (microphone) or electrical signals back into sound (loudspeaker).
A transducer is any device that converts one form of energy into another form. In the context of communication systems, an important example is a device that converts a sound (audio) signal into a corresponding electrical (voltage/current) signal, such as a microphone; the reverse conversion — electrical signal into sound — is performed by a loudspeaker. Transducers are essential at the input of a communication system (to generate an electrical message signal from the original information) and at the output (to convert the received electrical signal back into a form the user can perceive).
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- CBSE 2018Set ANNUAL1 markMCQQ.Which of the following devices converts message signals into equivalent electrical signals?(a) Converter(b) Transformer(c) Transducer(d) Inverter
›Reveal solutionSolution
A transducer is any device that converts a physical quantity or message (sound, pressure, light, etc.) into a proportional electrical signal, making it the device that turns a 'message' into an electrical form for transmission.
In a communication system, the message to be conveyed (such as a voice or an image) usually starts out as a non-electrical signal. Before it can be transmitted electronically, it must be converted into an equivalent electrical (voltage/current) signal. The device that performs this energy conversion is called a TRANSDUCER — for example, a microphone (sound to electrical signal) or a photodiode (light to electrical signal).
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- CBSE 2018Set ANNUAL1 markMCQQ.Meaning of "FAX" is -(a) Full Access Transmission(b) Facsimile Telegraphy(c) Factual Auto Access(d) Feed Auto Exchange
›Reveal solutionSolution
FAX = Facsimile Telegraphy — transmitting an exact reproduction of text/images over a channel.
FAX is short for 'facsimile', meaning an exact copy. In facsimile telegraphy, a document is scanned, converted to an electrical signal, transmitted over telephone or …
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