This is the Multiple Choice Questions in Chapter 12: Digital Modulation and Modems from the book Electronic Communication Systems by Roy Blake
See also: MCQ in Electronic Communication Systems by George Kennedy
Start Practice Exam Test Questions
Choose the letter of the best answer in each questions.
MULTIPLE CHOICE
1. FSK stands for:
a. Full-Shift Keying
b. Frequency-Shift Keying
c. Full-Signal Keying
d. none of the above
Answer: Option B
Solution:
2. PSK stands for:
a. Pulse-Signal Keying
b. Pulse-Shift Keying
c. Phase-Signal Keying
d. Phase-Shift Keying
Answer: Option D
Solution:
3. QAM stands for:
a. Quadrature Amplitude Modulation
b. Quadrature Amplitude Masking
c. Quadrature Amplitude Marking
d. none of the above
Answer: Option A
Solution:
4. In the equation I = ktB, I is measured in:
a. amperes
b. amperes per second
c. bits
d. bits per second
Answer: Option C
Solution:
5. In the equation C = 2Blog2M, M is the:
a. margin of noise
b. modulation index
c. number of possible states per symbol
d. maximum number of symbols per second
Answer: Option C
Solution:
6. An “eye pattern” shows a good channel when:
a. the eye is maximally open
b. the eye is maximally closed
c. the eye is half open
d. the eye alternately opens and closes
Answer: Option A
Solution:
7. What you see in an eye pattern is the effect of:
a. too many bits high
b. too many bits low
c. intermodulation distortion
d. intersymbol interference
Answer: Option D
Solution:
8. High-frequency radioteletype systems commonly use:
a. FSK
b. AFSK
c. PSK
d. QAM
Answer: Option A
Solution:
9. Instead of a single bit, a QPSK symbol contains:
a. a byte
b. 4 bits
c. a dibit
d. a Q-bit
Answer: Option C
Solution:
10. To reduce the need for linearity, π/4 DQPSK uses:
a. angles of 0, 90, 180, and 270 degrees
b. angles of 45, 135, 225, and 315 degrees
c. angles of π/4, 2π/4, 3π/4, and 4π/4
d. double phase-shift angles
Answer: Option B
Solution:
11. For QAM, a “constellation diagram” shows:
a. location of symbols in “symbol space”
b. separation of symbols in “symbol space”
c. effects of noise on symbols
d. all of the above
Answer: Option D
Solution:
12. For QAM, the two dimensions of its symbol space are:
a. amplitude and frequency
b. amplitude and phase angle
c. frequency and phase angle
d. I-bits and Q-bits
Answer: Option B
Solution:
13. The specs of the old Bell type 103 modem were:
a. 300 bps, full-duplex, FSK
b. 600 bps, full-duplex, FSK
c. 1200 bps, full-duplex, FSK
d. 1200 bps, half-duplex, FSK
Answer: Option A
Solution:
14. ITU is an abbreviation for:
a. International Telephony Unit
b. International Telephony Union
c. International Telecommunications Union
d. International Telecommunications Units
Answer: Option C
Solution:
15. The ITU is under the auspices of:
a. CCITT
b. the U.N.
c. IEEE
d. ANSI
Answer: Option B
Solution:
16. High-speed modems equalize the line to compensate for:
a. noise and interference
b. uneven phase and frequency response
c. low SNR
d. inconsistent bit rates at either end of channel
Answer: Option B
Solution:
17. The bits sent to allow equalization are called:
a. Gaussian bits
b. random bits
c. a training sequence
d. a random sequence
Answer: Option C
Solution:
18. The V.90 standard is issued by:
a. the EIA
b. the TIA
c. the ITU
d. the ISO
Answer: Option C
Solution:
19. MNP2, MNP3, MNP4, and MNP10 are all:
a. data-compression schemes
b. error-correction protocols
c. both a and b
d. none of the above
Answer: Option B
Solution:
20. MNP5 and V.42 bis are both:
a. data-compression schemes
b. error-correction protocols
c. both a and b
d. none of the above
Answer: Option A
Solution:
21. In RS-232, flow control is done using:
a. RTS/CTS handshake
b. XON/XOFF characters
c. both a and b
d. none of the above
Answer: Option C
Solution:
22. The official name for RS-232C is:
a. RS-232C
b. EIA-232D
c. ISO-232C/D
d. ANSI-232C
Answer: Option B
Solution:
23. In RS-232, a modem would be:
a. a DTR
b. a DSR
c. a DCE
d. a DTE
Answer: Option C
Solution:
24. In RS-232, a personal computer would be:
a. a DTR
b. a DSR
c. a DCE
d. a DTE
Answer: Option D
Solution:
25. On a DB-9 RS-232 connector, signal ground is pin:
a. 1
b. 3
c. 5
d. 7
Answer: Option C
Solution:
26. On a DB-25 RS-232 connector, signal ground is pin:
a. 1
b. 3
c. 5
d. 7
Answer: Option D
Solution:
27. The minimum lines required for RS-232 are:
a. TD and RD
b. TD, RD, and signal ground
c. TD, RD, DSR, and signal ground
d. TD, RD, RTS, CTS, and signal ground
Answer: Option B
Solution:
28. Hardware flow control uses:
a. XON and XOFF
b. TD and RD
c. RTS and CTS
d. DSR and DCD
Answer: Option C
Solution:
29. Software flow control uses:
a. XON and XOFF
b. TD and RD
c. RTS and CTS
d. DSR and DCD
Answer: Option A
Solution:
30. Which voltage represents a binary zero on an RS-232 data pin:
a. +15 volts
b. +12 volts
c. +9 volts
d. all of the above
Answer: Option D
Solution:
31. DSL stands for:
a. Data Signal Line
b. Digital Signal Line
c. Digital Subscriber Line
d. Double-Speed Loop
Answer: Option C
Solution:
32. ADSL stands for:
a. Asynchronous DSL
b. Asymmetrical DSL
c. Analog DSL
d. All DSL
Answer: Option B
Solution:
33. In a CATV system, HFC stands for:
a. Head Frequency Control
b. Hybrid Frequency Control
c. Hybrid Fiber-Coax
d. Hybrid Fiber Control
Answer: Option C
Solution:
34. In a CATV system, CMTS stands for:
a. Cable Modem Terminal Server
b. Cable Modem Transmission System
c. Cable Modem Terminal System
d. Cable Modem Transmission Server
Answer: Option A
Solution:
35. A “splitter” at the subscriber end is not required for:
a. Any DSL scheme
b. ADSL
c. ADSL Lite
d. none of the above
Answer: Option C
Solution:
COMPLETION
1. RTS means Request To ____________________.
Answer: Send
Solution:
2. The response to RTS is ____________________.
Answer: CTS
Solution:
3. FSK stands for Frequency-Shift ____________________.
Answer: Keying
Solution:
4. DSR stands for ____________________ Set Ready.
Answer: Data
Solution:
5. QAM stands for ____________________ Amplitude Modulation.
Answer: Quadrature
Solution:
6. The number of symbols per second is called the ____________________ rate.
Answer: baud
Solution:
7. The 2 bits of information in a QPSK symbol is called a ____________________.
Answer: dibit
Solution:
8. QPSK uses ____________________ different phase angles.
Answer: four
Solution:
9. DPSK stands for ____________________ PSK.
Answer: Delta
Solution:
10. The QAM amplitude-phase combinations are shown with a ____________________ diagram.
Answer: constellation
Solution:
11. ITU stands for International _________________________ Union.
Answer: Telecommunications
Solution:
12. In QAM modems, ____________________ coding adds extra bits to improve performance on a noisy line.
Answer: Trellis
Solution:
13. ____________________ is used in a high-speed modem to compensate for uneven frequency and phase response on a line.
Answer: Equalization
Solution:
14. The maximum allowed speed for a modem on a dial-up line is about ____________________ bps.
Answer: 54k
Solution:
15. The nominal maximum speed on an RS-232 cable is ____________________ bps.
Answer: 20k
Solution:
16. In RS-232, the ____________________ line is asserted when the analog carrier from another modem is being received.
Answer:
CD
DCD
RLSD
Solution:
17. Between hardware flow control and software flow control, ____________________ flow control is preferred.
Answer: hardware
Solution:
18. A voltage higher than ____________________ volts should be considered a high on an RS-232 receiver.
Answer: 3
Solution:
19. A ____________________ modem cable is used to connect two DTEs via their serial ports.
Answer: null
Solution:
20. ADSL stands for ____________________ DSL.
Answer: Asymmetrical
Solution:
21. A typical CATV system is organized as a ____________________ network.
Answer: tree
Solution:
22. In a CATV system using cable modems, a ____________________ is used to put several channels of data onto a fiber-optic backbone.
Answer: CMTS
Solution:
23. ____________________ is the process of synchronizing transmitted data from cable modems to a CMTS.
Answer: Ranging
Solution:
24. ____________________ systems send high-speed data over a POTS line while sharing the line with dialup service.
Answer: ADSL
Solution:
25. The ____________________ version of ADSL does not require a splitter at the subscriber end.
Answer: lite
Solution:
26. ____________________ modulation divides the line bandwidth into many narrow bands called tones or bins for ADSL.
Answer: DMT
Solution:
27. A DSLAM is a DSL Access ____________________.
Answer: Multiplexer
Solution:
SHORT ANSWER
1. Calculate the bits per second capacity of a system sending 1000 symbols per second with 16 possible states per symbol.
Answer: 4000
Solution:
2. How many points will be on the constellation diagram of a QAM system using 8 phase angles and 2 amplitude levels?
Answer: 16
Solution:
3. A CATV system has 100 cable-modem customers sharing a single channel with a data rate of 36 Mbps. If half the modems are active at any given time, what bit rate can a customer expect?
Answer: 720 kbps
Solution:
4. A DMT system uses 4.3-kHz bins on a 1-MHz cable. Approximately how many bins are there?
Answer: 230
Solution:
5. Assuming a maximum symbol rate of 400 per second, how many possible states must a symbol have to achieve a data rate of 1200 bps?
Answer: 8
Solution:
Complete List of MCQ in Electronic Communication Systems by Blake
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