Elements of a communication system - class-XII
elements of a communication system
Questions
The wave used by artificial satellites for communication is
- Microwaves
- Infrared rays
- Radio rays
- X-rays
In sky wave communication which of the frequency will be reflected back by the ionospheric layer having electron density $4 \times 10 ^ { 6 } / \mathrm { m } ^ { 3 }$
- $19 \times 10 ^ { 3 } \mathrm { Hz }$
- $9 \times 10 ^ { 3 } H z$
- $31 \times 10 ^ { 3 } \mathrm { Hz }$
- $20 \times 10 ^ { 3 } \mathrm { Hz }$
The examples of broadcast are
A) radio B) television
C) telephony D) internet
- A & B
- A, B & D
- A,B & C
- B & D
A digital signal
- is less reliable than analog signal
- is more reliable than analog signal
- is equally reliable as the analog signal
- Not at all reliable
Statement A: If the antenna is vertical,a vertically polarised EM wave is radiated
Statement B: The vertically polarised EM wave has electrical variations in the vertical plane
- A is true but B is false
- A is false but B is true
- A and B are false
- A and B are true
An antenna serves the following purpose :
- Converts AF wave to RF wave
- Converts RF signal into electromagnetic energy
- Converts the guided EM waves into free space EM waves and vice versa
- Superimposes AF wave on RF wave
The concepts of communication are
a) mode of communication
b) need for modulation
c) types of modulation
d) detection of modulated wave
- a, b, c are true
- b, c, d are true
- c, d, a are true
- a, b, c & d are true
Buffer amplifier is used at the transmitting end to
- feed carrier frequency to master oscillator
- amplify carrier frequency
- mix modulating signal with carrier frequency
- isolate master oscillator from other stages of transmitter.
The science of communication involving long distances is known as
- mass-communication
- distant-communication
- tele-communication
- trans-communication
The useful message that is conveyed during communication is known as
- text
- electric signal
- bytes
- information
The term channel is used to indicate
- the amplitude range allocated to a given source
- the frequency range allocated to a given source
- the voltage-range allocated to a given source
- all of the above
Consider telecommunication through optical fibres. Which of the following statement is not true?
- Optical fibres may have homogenous core with a suitable cladding.
- Optical fibres can be graded refractive index.
- Optical fibres are subject to electromagnetic interference from outside.
- Optical fibres have extremely low transmission loss.
Without which of the following a generalized block diagram of communication system is incomplete?
- Channel
- Receiver
- Transmitter
- All of the above
What are the three essential part of a communication system?
- transmitter, channel and receiver
- transmitter, information source and receiver
- information source ,transmitter and channel
- transmitter , noise and channel
Which of the following is/are the example(s) of real life telecommunication system?
- Optical fiber communication
- Microwave communication
- Coaxial cable communication
- None of the above
In which year, the radio broadcasting had started in India?
- 1925
- 1926
- 1927
- 1928
The waves used in telecommunication are
- Infrared
- Ultraviolet
- Microwaves
- Cosmic rays
A receiver in a communication system must have
- Pick-up antenna
- Demodulator
- Amplifier
- All of these
When two or more signals share a common channel, it is called:
- sub-channeling
- signal switching
- SINAD
- multiplexing
A complete communication system must include:
- a transmitter and receiver
- a transmitter, a receiver, and a channel
- a transmitter, a receiver, and a spectrum analyzer
- a multiplexer, a demultiplexer, and a channel
An antenna is a device that converts
- electromagnetic energy into radio frequency
signal - radio frequency signal into electromagnetic
energy - guided electromagnetic waves into free space
electromagnetic waves - free space electromagnetic waves into guided
electromagnetic waves
Basically, a communication system is a
- Transmitter
- Receiver
- Messenger
- all of these
The collection of communication line and routers form the:
- Router
- Bridge
- Submet
- Packet
The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot ?
- 2250 kHz
- 2900 kHz
- 2750 kHz
- 2000 kHz
To double the covering range of a TV transmission tower, its height should be multiplied by :
- 2
- 4
- $
\sqrt{2}
$ - $
\frac{1}{\sqrt{2}}
$
The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot ?
- 2250 kHz
- 2900 kHz
- 2750 kHz
- 2000 kHz