Electronics and Communication Related Interview Questions - 2
21) How many satellites are required to cover the earth?
3 satellites are required to cover the entire earth, which is placed at 120 degree to each other.
The life span of the satellite is about 15 years.
22) What is a repeater?
A repeater is an electronic device that receives a signal and retransmits it at a higher level
and/or higher power, or onto the other side of an obstruction, so that the signal can cover
longer distances without degradation.
23) What is attenuation?
Attenuation is the reduction in amplitude and intensity of a signal.
Signals may attenuate exponentially by transmission through a medium, or by increments calculated in electronic circuitry or set by variable controls.
Attenuation is an important property in telecommunications and ultrasound applications because of its importance in determining signal strength as a function of distance.
Attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc) and is represented by the attenuation coefficient of the medium in question.
24) What is multiplexing?
Multiplexing (known as muxing) is a term used to refer to a processwhere multiple analog
message signals or digital data streams are combined into one signal over a shared medium.
The aim is to share an expensive resource. For example, in telecommunications, several
phone calls may be transferred using one wire.
25) What is CDMA, TDMA, FDMA?
Code division multiple access (CDMA) is a channel access methodutilized by various radio
communication technologies.
CDMA employsspread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel.
By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it byfrequency.
An analogy to the problem of multiple access is a room (channel) in which people wish to
communicate with each other.
To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division).
In CDMA, they would speak different languages.
People speaking the same language can understand each other, but not other people.
Similarly, in radio CDMA, each group of users is given a shared code. \
Many codes occupy the same channel, but only users associated with a particular code can understand each other.
26) Difference between CDMA and GSM.
These are the two different means of mobile communication being presently used worldwide.
The basic difference lies in the Multiplexing method used in the aerial communication i.e.
from Mobile Tower to your mobile and vice versa.
CDMA uses Code Division Multiple Access as the name itself indicates,
for example you are in a hall occupied with number of people speaking different language. You will find that the one language you know will be heard by you and the others will be treated like noise. In the same manner each CDMA mobile communication takes place with a "code" communicating
between them and the other end if one is knowing that code then only it can listen to the data
being transmitted i.e. the communication is in the coded form.
On the other hand GSM (Global System for Mobile Communications) uses
narrowband TDMA, which allows eight simultaneous calls on the same radio frequency.
TDMA works by dividing a radio frequency into time slots and then allocating slots to
multiple calls. In this way, a single frequency can support multiple, simultaneous data
channels.
27) What is an Amplifier?
An electronic device or electrical circuit that is used to boost (amplify) the power, voltage or
current of an applied signal.
28) What is Barkhausen criteria?
Barkhausen criteria, without which you will not know which conditions, are to be satisfied
for oscillations.
“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product
of the transfer gain of the amplifier and the magnitude of the feedback factor of the feedback
network ( the magnitude of the loop gain ) are less than unity”.
The condition of unity loop gain -Aβ = 1 is called the Barkhausencriterion. This condition
implies that | Aβ|= 1and that the phase of - Aβ is zero.
29) Explain Full duplex and half duplex.
Full duplex refers to the transmission of data in two directions simultaneously.
For example,
a telephone is a full-duplex devicebecause both parties can talk at once.
In contrast, a walkietalkie is a half-duplex device because only one party can transmit at a time.
Most modems have a switch that lets you choose between full-duplex and half-duplex modes.
The choice depends on which communications program you are running.
In full-duplex mode, data you transmit does not appear on yourscreen until it has been
received and sent back by the other party.
This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
30) What is a feedback? And explain different types of feedback.
Feedback is a process whereby some proportion of the output signal of a system is passed
(fed back) to the input. This is often used to control the dynamic behaviour of the system.
Types of feedback:
Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizes
operation).
Negative feedback feeds part of a system's output, inverted, into the system's input; generally with the result that fluctuations are attenuated.
Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as
"cumulative causation", is a feedback loop system in which the system responds
to perturbation (Aperturbation means a system, is an alteration of function, induced by
external or internal mechanisms) in the same direction as the perturbation.
In contrast, a system that responds to the perturbation in the opposite direction is called a negative
feedback system.
Bipolar feedback: which can either increase or decrease output.
31) Advantages of negative feedback over positive feedback.
Much attention has been given by researchers to negative feedback processes, because
negative feedback processes lead systems towards equilibrium states. Positive feedback
reinforces a given tendency of a system and can lead a system away from equilibrium states,
possibly causing quite unexpected results.
32) Example for negative feedback and positive feedback.
Example for –ve feedback is ---Amplifiers
And for +ve feedback is – Oscillators
33) What is Oscillator?
An oscillator is a circuit that creates a waveform output from a direct current input. The two
main types of oscillator are harmonic and relaxation.
The harmonic oscillators have smooth curved waveforms, while relaxation oscillators have waveforms with sharp changes.
34) What is a transducer and transponder?
A transducer is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer.
In telecommunication, the term transponder (short-forTransmitter-responder and sometimes
abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
• An automatic device that receives, amplifies, andretransmits a signal on a
different frequency (see alsobroadcast translator).
• An automatic device that transmits a predetermined messagein response to a
predefined received signal.
• A receiver-transmitter that will generate a reply signal upon
proper electronic interrogation.
A communications satellite’s channels are called transponders, because each is a
separate transceiver or repeater.
35) What is an Integrated Circuit?
An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a
silicon chip. Their main advantages are low cost, low power, high performance, and very
small size.
36) What is crosstalk?
Crosstalk is a form of interference caused by signals in nearby conductors. The most common
example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in
radios, televisions, networking equipment, and even electric guitars.
37) What is a rectifier?
A rectifier changes alternating current into direct current.
This process is called rectification.
The three main types of rectifier are the half-wave, full-wave, and bridge.
A rectifier is the opposite of an inverter, which changes direct current into alternating current.
HWR- The simplest type is the half-wave rectifier, which can be made with just one diode.
When the voltage of the alternating current is positive, the diode becomes forward-biased and
current flows through it.
When the voltage is negative, the diode is reverse-biased and the current stops. The result is a clipped copy of the alternating current waveform with only positive voltage, and an average voltage that is one third of the peak input voltage.
This pulsating direct current is adequate for some components, but others require a more steady
current. This requires a full-wave rectifier that can convert both parts of the cycle to positive
voltage.
FWR- The full-wave rectifier is essentially two half-wave rectifiers, and can be made with
two diodes and an earthed centre tap on the transformer.
The positive voltage half of the cycle flows through one diode, and the negative half flows through the other.
The centre tap allows the circuit to be completed because current cannot flow through the other diode.
The result is still a pulsating direct current but with just over half the input peak voltage, and
double the frequency.
38) What is resistor?
A resistor is a two-terminal electronic component that opposes anelectric current by
producing a voltage drop between its terminals in proportion to the current, that is, in
accordance with Ohm's law: V= IR.
39) What is capacitor?
A capacitor is an electrical/electronic device that can store energyin the electric field between
a pair of conductors (called "plates").
The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.
Capacitors are often used in electric and electronic circuits asenergy-storage devices.
They can also be used to differentiate between high-frequency and low-frequency signals. This
property makes them useful in electronic filters.
Capacitors are occasionally referred to as condensers.
This term is considered archaic in English, but most other languages use acognate of condenser to refer to a capacitor.
40) What is inductor?
An inductor is a passive electrical device employed in electrical circuits for its property
of inductance. An inductor can take many forms.
3 satellites are required to cover the entire earth, which is placed at 120 degree to each other.
The life span of the satellite is about 15 years.
22) What is a repeater?
A repeater is an electronic device that receives a signal and retransmits it at a higher level
and/or higher power, or onto the other side of an obstruction, so that the signal can cover
longer distances without degradation.
23) What is attenuation?
Attenuation is the reduction in amplitude and intensity of a signal.
Signals may attenuate exponentially by transmission through a medium, or by increments calculated in electronic circuitry or set by variable controls.
Attenuation is an important property in telecommunications and ultrasound applications because of its importance in determining signal strength as a function of distance.
Attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc) and is represented by the attenuation coefficient of the medium in question.
24) What is multiplexing?
Multiplexing (known as muxing) is a term used to refer to a processwhere multiple analog
message signals or digital data streams are combined into one signal over a shared medium.
The aim is to share an expensive resource. For example, in telecommunications, several
phone calls may be transferred using one wire.
25) What is CDMA, TDMA, FDMA?
Code division multiple access (CDMA) is a channel access methodutilized by various radio
communication technologies.
CDMA employsspread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel.
By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it byfrequency.
An analogy to the problem of multiple access is a room (channel) in which people wish to
communicate with each other.
To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division).
In CDMA, they would speak different languages.
People speaking the same language can understand each other, but not other people.
Similarly, in radio CDMA, each group of users is given a shared code. \
Many codes occupy the same channel, but only users associated with a particular code can understand each other.
26) Difference between CDMA and GSM.
These are the two different means of mobile communication being presently used worldwide.
The basic difference lies in the Multiplexing method used in the aerial communication i.e.
from Mobile Tower to your mobile and vice versa.
CDMA uses Code Division Multiple Access as the name itself indicates,
for example you are in a hall occupied with number of people speaking different language. You will find that the one language you know will be heard by you and the others will be treated like noise. In the same manner each CDMA mobile communication takes place with a "code" communicating
between them and the other end if one is knowing that code then only it can listen to the data
being transmitted i.e. the communication is in the coded form.
On the other hand GSM (Global System for Mobile Communications) uses
narrowband TDMA, which allows eight simultaneous calls on the same radio frequency.
TDMA works by dividing a radio frequency into time slots and then allocating slots to
multiple calls. In this way, a single frequency can support multiple, simultaneous data
channels.
27) What is an Amplifier?
An electronic device or electrical circuit that is used to boost (amplify) the power, voltage or
current of an applied signal.
28) What is Barkhausen criteria?
Barkhausen criteria, without which you will not know which conditions, are to be satisfied
for oscillations.
“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product
of the transfer gain of the amplifier and the magnitude of the feedback factor of the feedback
network ( the magnitude of the loop gain ) are less than unity”.
The condition of unity loop gain -Aβ = 1 is called the Barkhausencriterion. This condition
implies that | Aβ|= 1and that the phase of - Aβ is zero.
29) Explain Full duplex and half duplex.
Full duplex refers to the transmission of data in two directions simultaneously.
For example,
a telephone is a full-duplex devicebecause both parties can talk at once.
In contrast, a walkietalkie is a half-duplex device because only one party can transmit at a time.
Most modems have a switch that lets you choose between full-duplex and half-duplex modes.
The choice depends on which communications program you are running.
In full-duplex mode, data you transmit does not appear on yourscreen until it has been
received and sent back by the other party.
This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
30) What is a feedback? And explain different types of feedback.
Feedback is a process whereby some proportion of the output signal of a system is passed
(fed back) to the input. This is often used to control the dynamic behaviour of the system.
Types of feedback:
Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizes
operation).
Negative feedback feeds part of a system's output, inverted, into the system's input; generally with the result that fluctuations are attenuated.
Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as
"cumulative causation", is a feedback loop system in which the system responds
to perturbation (Aperturbation means a system, is an alteration of function, induced by
external or internal mechanisms) in the same direction as the perturbation.
In contrast, a system that responds to the perturbation in the opposite direction is called a negative
feedback system.
Bipolar feedback: which can either increase or decrease output.
31) Advantages of negative feedback over positive feedback.
Much attention has been given by researchers to negative feedback processes, because
negative feedback processes lead systems towards equilibrium states. Positive feedback
reinforces a given tendency of a system and can lead a system away from equilibrium states,
possibly causing quite unexpected results.
32) Example for negative feedback and positive feedback.
Example for –ve feedback is ---Amplifiers
And for +ve feedback is – Oscillators
33) What is Oscillator?
An oscillator is a circuit that creates a waveform output from a direct current input. The two
main types of oscillator are harmonic and relaxation.
The harmonic oscillators have smooth curved waveforms, while relaxation oscillators have waveforms with sharp changes.
34) What is a transducer and transponder?
A transducer is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer.
In telecommunication, the term transponder (short-forTransmitter-responder and sometimes
abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
• An automatic device that receives, amplifies, andretransmits a signal on a
different frequency (see alsobroadcast translator).
• An automatic device that transmits a predetermined messagein response to a
predefined received signal.
• A receiver-transmitter that will generate a reply signal upon
proper electronic interrogation.
A communications satellite’s channels are called transponders, because each is a
separate transceiver or repeater.
35) What is an Integrated Circuit?
An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a
silicon chip. Their main advantages are low cost, low power, high performance, and very
small size.
36) What is crosstalk?
Crosstalk is a form of interference caused by signals in nearby conductors. The most common
example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in
radios, televisions, networking equipment, and even electric guitars.
37) What is a rectifier?
A rectifier changes alternating current into direct current.
This process is called rectification.
The three main types of rectifier are the half-wave, full-wave, and bridge.
A rectifier is the opposite of an inverter, which changes direct current into alternating current.
HWR- The simplest type is the half-wave rectifier, which can be made with just one diode.
When the voltage of the alternating current is positive, the diode becomes forward-biased and
current flows through it.
When the voltage is negative, the diode is reverse-biased and the current stops. The result is a clipped copy of the alternating current waveform with only positive voltage, and an average voltage that is one third of the peak input voltage.
This pulsating direct current is adequate for some components, but others require a more steady
current. This requires a full-wave rectifier that can convert both parts of the cycle to positive
voltage.
FWR- The full-wave rectifier is essentially two half-wave rectifiers, and can be made with
two diodes and an earthed centre tap on the transformer.
The positive voltage half of the cycle flows through one diode, and the negative half flows through the other.
The centre tap allows the circuit to be completed because current cannot flow through the other diode.
The result is still a pulsating direct current but with just over half the input peak voltage, and
double the frequency.
38) What is resistor?
A resistor is a two-terminal electronic component that opposes anelectric current by
producing a voltage drop between its terminals in proportion to the current, that is, in
accordance with Ohm's law: V= IR.
39) What is capacitor?
A capacitor is an electrical/electronic device that can store energyin the electric field between
a pair of conductors (called "plates").
The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.
Capacitors are often used in electric and electronic circuits asenergy-storage devices.
They can also be used to differentiate between high-frequency and low-frequency signals. This
property makes them useful in electronic filters.
Capacitors are occasionally referred to as condensers.
This term is considered archaic in English, but most other languages use acognate of condenser to refer to a capacitor.
40) What is inductor?
An inductor is a passive electrical device employed in electrical circuits for its property
of inductance. An inductor can take many forms.
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