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Question 1 of 60 Quiz ID: q1

What is the primary difference between encoding and modulation as defined in the lecture?

Encoding is for digital signals, modulation is for analog signals

Encoding prepares a signal for wire/fiber, modulation modifies a carrier signal

Encoding increases data rate, modulation decreases bandwidth

Encoding uses multiple levels, modulation uses only two levels

Question 2 of 60 Quiz ID: q2

In NRZ-L encoding, what characterizes the signal representation?

Transition at the beginning of each bit period indicates the bit value

Two different voltage levels are used, constant during the bit interval

The signal returns to zero voltage after each bit transmission

Alternating positive and negative pulses represent binary 1s

Question 3 of 60 Quiz ID: q3

What is the key advantage of differential encoding schemes like NRZI?

They require less bandwidth than NRZ-L

They eliminate the DC component completely

They provide more reliable detection of transitions rather than levels

They allow each signal element to represent multiple bits

Question 4 of 60 Quiz ID: q4

Which characteristic is a significant disadvantage of NRZ encoding for signal transmission?

High bandwidth requirements

Lack of synchronization capability

Susceptibility to noise

Complex implementation

Question 5 of 60 Quiz ID: q5

In Bipolar-AMI encoding, how are binary 1s represented?

By alternating positive and negative pulses

By the absence of line signal

By a constant positive voltage

By mid-bit transitions

Question 6 of 60 Quiz ID: q6

What is the primary trade-off when using multilevel binary encoding schemes like Bipolar-AMI?

They require more complex hardware implementation

They are less bandwidth efficient than NRZ

They require approximately 3dB more signal power for the same error probability

They cannot be used for long-distance transmission

Question 7 of 60 Quiz ID: q7

How does Manchester encoding provide built-in synchronization?

By including a separate clock signal with the data

Through a transition in the middle of each bit period

By using alternating voltage levels for each bit

Through special synchronization bits inserted periodically

Question 8 of 60 Quiz ID: q8

What is the key difference between Manchester and Differential Manchester encoding?

Manchester uses two voltage levels, Differential Manchester uses three

Differential Manchester is a differential encoding scheme

Manchester has higher bandwidth requirements

Differential Manchester provides better error detection

Question 9 of 60 Quiz ID: q9

What problem does scrambling techniques like B8ZS and HDB3 primarily address?

Reducing bandwidth requirements

Eliminating the DC component and ensuring adequate transitions

Increasing data rate beyond the Nyquist limit

Providing error correction capability

Question 10 of 60 Quiz ID: q10

In B8ZS coding, how does the receiver identify and interpret the special substitution sequence?

By detecting two violations of the AMI code pattern

Through a special start delimiter before the sequence

By recognizing three consecutive zero pulses

Through a separate control channel

Question 11 of 60 Quiz ID: q11

What is the primary reason for using modulation techniques like ASK, FSK, and PSK in telephone systems?

To increase the data rate beyond the channel capacity

To convert digital data for transmission over analog voice-grade lines

To provide error correction capability

To encrypt the data for security

Question 12 of 60 Quiz ID: q12

Why is ASK generally considered inefficient compared to other modulation schemes?

It requires more complex receiver circuitry

It is highly susceptible to sudden gain changes and noise

It cannot be used at data rates above 1200bps

It requires wider bandwidth than other techniques

Question 13 of 60 Quiz ID: q13

What advantage does FSK have over ASK in terms of error susceptibility?

FSK is less susceptible to errors caused by amplitude variations

FSK requires less bandwidth than ASK

FSK can achieve higher data rates on voice-grade lines

FSK is easier to implement than ASK

Question 14 of 60 Quiz ID: q14

In PSK, what characteristic of the carrier signal is altered to represent data?

Amplitude

Frequency

Phase

Wavelength

Question 15 of 60 Quiz ID: q15

What is the key advantage of QPSK over basic PSK?

It requires less power for the same error rate

It is less susceptible to phase noise

Each signal element represents more than one bit

It provides built-in error correction

Question 16 of 60 Quiz ID: q16

How does QAM achieve higher data rates compared to simple modulation schemes?

By using multiple carriers simultaneously

By combining amplitude and phase modulation on the same carrier

Through advanced error correction techniques

By operating at much higher frequencies

Question 17 of 60 Quiz ID: q17

According to the Nyquist theorem in PCM, what sampling rate is required for a signal with maximum frequency of 4000Hz?

4000 samples per second

8000 samples per second

16000 samples per second

32000 samples per second

Question 18 of 60 Quiz ID: q18

What is quantizing error in PCM, and why does it occur?

Error caused by sampling at insufficient rates

Noise introduced during the analog-to-digital conversion process

The difference between the actual analog value and the nearest quantization level

Errors introduced during digital transmission

Question 19 of 60 Quiz ID: q19

What is the data rate of standard PCM for telephone voice transmission?

32 kbps

56 kbps

64 kbps

128 kbps

Question 20 of 60 Quiz ID: q20

How does nonlinear encoding (companding) improve PCM performance?

By increasing the sampling rate beyond Nyquist

By using unevenly spaced quantization levels to reduce overall distortion

Through error correction coding

By eliminating the need for quantization

Question 21 of 60 Quiz ID: q21

In delta modulation, what is 'slope overload noise'?

Noise caused by excessive quantization levels

Distortion that occurs when the analog signal changes too rapidly for the staircase to follow

Interference between adjacent samples

Noise introduced during the sampling process

Question 22 of 60 Quiz ID: q22

What is the fundamental principle behind delta modulation?

Encoding the difference between consecutive samples rather than absolute values

Using variable sampling rates based on signal activity

Eliminating the need for quantization

Transmitting only significant changes in the signal

Question 23 of 60 Quiz ID: q23

Why are analog signals modulated onto higher frequency carriers for transmission?

To reduce the signal power requirements

To allow for frequency division multiplexing and more efficient transmission

To make the signals digital for error correction

To compress the analog data

Question 24 of 60 Quiz ID: q24

In amplitude modulation (AM), what does the modulation index represent?

The ratio of carrier frequency to modulating signal frequency

The depth of modulation or how much the carrier amplitude varies

The number of sidebands produced

The bandwidth efficiency of the modulation

Question 25 of 60 Quiz ID: q25

What mathematical relationship describes a phase modulated signal?

s(t) = A_c[1 + k·m(t)]cosω_ct

s(t) = A_ccos(ω_ct + Δ_pm(t))

s(t) = A_ccos(2πΔ_f∫m(τ)dτ)

s(t) = A_c[1 + k·m(t)]sinω_ct

Question 26 of 60 Quiz ID: q26

How does frequency modulation (FM) differ from phase modulation (PM) in terms of the relationship with the modulating signal?

FM varies frequency proportionally to the modulating signal, PM varies phase proportionally

FM varies phase proportionally to the modulating signal, PM varies frequency proportionally

FM uses amplitude variations, PM uses phase variations

FM is digital, PM is analog

Question 27 of 60 Quiz ID: q27

Which encoding scheme is specifically mentioned as being used for magnetic recording?

Manchester encoding

Bipolar-AMI

NRZ

Differential Manchester

Question 28 of 60 Quiz ID: q28

What is the fundamental difference between baseband and broadband transmission?

Baseband is digital, broadband is analog

Baseband carries one signal at a time, broadband carries multiple signals simultaneously

Baseband uses higher frequencies than broadband

Baseband requires modulation, broadband does not

Question 29 of 60 Quiz ID: q29

In the context of signal interpretation, what three factors affect successful interpretation of signals?

Voltage level, bit duration, and encoding scheme

Signal-to-noise ratio, data rate, and bandwidth

Carrier frequency, modulation index, and bandwidth

Sampling rate, quantization levels, and compression ratio

Question 30 of 60 Quiz ID: q30

What problem common to both NRZ and multilevel binary encoding does biphase encoding (Manchester) solve?

High bandwidth requirements

DC component and lack of synchronization

Complex implementation

Susceptibility to noise

Question 31 of 60 Quiz ID: q31

In Differential Manchester encoding, how is a binary 0 represented?

By a transition at the start of the bit period

By no transition at the start of the bit period

By a low-to-high transition in the middle of the bit period

By a high-to-low transition in the middle of the bit period

Question 32 of 60 Quiz ID: q32

What is the primary purpose of the mid-bit transition in standard Manchester encoding?

To represent the binary value of the bit

To serve as both clock and data information

To eliminate the DC component

To provide error detection capability

Question 33 of 60 Quiz ID: q33

Why is HDB3 called 'High Density Bipolar 3 Zeros'?

It can represent three zeros with a single pulse

It replaces strings of four zeros with special sequences

It uses three different voltage levels for encoding

It requires at least three zeros between consecutive ones

Question 34 of 60 Quiz ID: q34

What advantage do B8ZS and HDB3 scrambling techniques provide over basic Bipolar-AMI?

Higher data rates for the same bandwidth

Better error correction capability

Elimination of long sequences of zero level line signal

Simpler implementation circuitry

Question 35 of 60 Quiz ID: q35

In analog modulation, what is the relationship between the carrier frequency and the modulating signal frequency?

The carrier frequency must be exactly twice the highest modulating frequency

The carrier frequency is usually much greater than the highest modulating frequency

The carrier frequency should be equal to the modulating frequency for efficiency

The carrier frequency is typically lower than the modulating frequency

Question 36 of 60 Quiz ID: q36

What does the envelope represent in amplitude modulation?

The highest frequency component of the modulated signal

The pattern of the original modulating signal

The bandwidth of the transmitted signal

The phase relationship between carrier and sidebands

Question 37 of 60 Quiz ID: q37

Which digital-to-analog modulation technique is mentioned as being used over optical fiber?

Amplitude Shift Keying (ASK)

Frequency Shift Keying (FSK)

Phase Shift Keying (PSK)

Quadrature Amplitude Modulation (QAM)

Question 38 of 60 Quiz ID: q38

What is the key advantage of multiple FSK over binary FSK?

Higher resistance to noise

More bandwidth efficiency

Simpler implementation

Lower power consumption

Question 39 of 60 Quiz ID: q39

In the performance comparison of digital-to-analog modulation schemes, how do PSK and QPSK compare to ASK and FSK in terms of bit error rate?

They have approximately 3dB superior performance in the presence of noise

They have approximately 3dB worse performance in the presence of noise

They have identical performance to ASK and FSK

Their performance depends on the carrier frequency used

Question 40 of 60 Quiz ID: q40

What is the relationship between ASK/PSK bandwidth and bit rate?

Bandwidth is inversely proportional to bit rate

Bandwidth is directly related to bit rate

Bandwidth is independent of bit rate

Bandwidth decreases as bit rate increases

Question 41 of 60 Quiz ID: q41

In PCM, what is the purpose of the PAM (Pulse Amplitude Modulation) stage?

To quantize the analog samples

To create discrete-time but continuous-amplitude samples

To encode the samples into binary format

To compress the digital data

Question 42 of 60 Quiz ID: q42

What is the significance of the 4kHz frequency limit for voice data in PCM?

It represents the maximum frequency that can be quantized without error

It determines the minimum sampling rate required by the Nyquist theorem

It is the standard bandwidth allocation for telephone channels

It represents the cutoff frequency for analog filters used in telephony

Question 43 of 60 Quiz ID: q43

Why does delta modulation typically require higher sampling rates than PCM for comparable quality?

Because it uses only one bit per sample instead of multiple bits

Because it requires oversampling to avoid slope overload

Because it uses a more complex quantization scheme

Because it includes error correction overhead

Question 44 of 60 Quiz ID: q44

What is the fundamental mathematical operation in frequency modulation?

Multiplication of the carrier with the modulating signal

Integration of the modulating signal

Differentiation of the carrier signal

Addition of the modulating signal to the carrier phase

Question 45 of 60 Quiz ID: q45

Which encoding scheme is used by IEEE 802.3 (Ethernet)?

NRZ-L

Manchester

Differential Manchester

Bipolar-AMI

Question 46 of 60 Quiz ID: q46

Which encoding scheme is used by IEEE 802.5 (Token Ring)?

NRZ-L

Manchester

Differential Manchester

Bipolar-AMI

Question 47 of 60 Quiz ID: q47

In the context of signal transmission, what does 'band' measure?

The data rate in bits per second

The modulation rate in signal elements per second

The bandwidth in Hertz

The signal-to-noise ratio in decibels

Question 48 of 60 Quiz ID: q48

What is the term for the time taken for a transmitter to emit a single bit?

Bit rate

Modulation period

Bit duration or length

Signal element interval

Question 49 of 60 Quiz ID: q49

In polar signaling, how are the two logic states typically represented?

Both states use positive voltage but different amplitudes

One state uses positive voltage, the other uses negative voltage

Both states use the same voltage but different frequencies

One state uses voltage, the other uses zero voltage

Question 50 of 60 Quiz ID: q50

What is the key difference between unipolar and polar signaling?

Unipolar uses one voltage level, polar uses two voltage levels of opposite signs

Unipolar is for digital data, polar is for analog data

Unipolar has higher bandwidth efficiency than polar

Unipolar provides better synchronization than polar

Question 51 of 60 Quiz ID: q51

What problem common to many encoding schemes does scrambling specifically address?

High power consumption

Limited maximum data rate

Sequences that produce constant voltage

Complex receiver design

Question 52 of 60 Quiz ID: q52

In the PCM example with 4-bit quantization, how many quantization levels are available?

8 levels

16 levels

32 levels

256 levels

Question 53 of 60 Quiz ID: q53

What is the primary advantage of using 8-bit samples in PCM instead of 4-bit samples?

Higher data rate

Reduced quantizing error

Lower bandwidth requirements

Simpler implementation

Question 54 of 60 Quiz ID: q54

In delta modulation, what determines whether the staircase function moves up or down?

The absolute value of the analog signal

Whether the analog signal is above or below the current staircase value

The slope of the analog signal

The frequency of the analog signal

Question 55 of 60 Quiz ID: q55

What is the main reason for modulating analog data onto analog signals?

To convert them to digital format

To allow frequency division multiplexing

To reduce their bandwidth requirements

To add error correction capability

Question 56 of 60 Quiz ID: q56

In QAM, how are two independent signals transmitted simultaneously on the same carrier?

By using different encryption keys for each signal

By using two copies of the carrier phase-shifted by 90°

By time-division multiplexing the signals

By using different modulation techniques for each signal

Question 57 of 60 Quiz ID: q57

What is the primary application mentioned for QAM in the lecture?

Ethernet networks

Optical fiber communication

Asymmetric Digital Subscriber Line (ADSL)

Satellite communication

Question 58 of 60 Quiz ID: q58

What does the term 'mark' and 'space' refer to in digital signaling?

Start and stop bits in asynchronous transmission

Binary 1 and binary 0 respectively

The highest and lowest voltage levels

Synchronization patterns in data frames

Question 59 of 60 Quiz ID: q59

What is the key characteristic that distinguishes baseband transmission of analog signals?

It uses the original frequency range before modulation

It requires digital encoding of the analog signal

It uses higher frequencies than broadband transmission

It allows multiple signals on the same channel

Question 60 of 60 Quiz ID: q60

In the context of signal elements, what does each pulse represent in digital signaling?

A single bit of data

A signal element that may represent one or more bits

A synchronization marker

A voltage level transition

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