Blake: MCQ in Digital Modulation and Modems

(Last Updated On: January 9, 2018)
Blake: MCQs in Digital Modulation and Modems

This is the Multiple Choice Questions in Chapter 12: Digital Modulation and Modems from the book Electronic Communication Systems by Roy BlakeBlake: MCQ in Digital Modulation and Modems. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

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

ANS: B

2. PSK stands for:

  • a. Pulse-Signal Keying
  • b. Pulse-Shift Keying
  • c. Phase-Signal Keying
  • d. Phase-Shift Keying

ANS: D

3. QAM stands for:

  • a. Quadrature Amplitude Modulation
  • b. Quadrature Amplitude Masking
  • c. Quadrature Amplitude Marking
  • d. none of the above

ANS: A

4. In the equation I = ktB, I is measured in:

  • a. amperes
  • b. amperes per second
  • c. bits
  • d. bits per second

ANS: C

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

ANS: C

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

ANS: A

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

ANS: D

8. High-frequency radioteletype systems commonly use:

  • a. FSK
  • b. AFSK
  • c. PSK
  • d. QAM

ANS: A

9. Instead of a single bit, a QPSK symbol contains:

  • a. a byte
  • b. 4 bits
  • c. a dibit
  • d. a Q-bit

ANS: C

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

ANS: B

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

ANS: D

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

ANS: B

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

ANS: A

14. ITU is an abbreviation for:

  • a. International Telephony Unit
  • b. International Telephony Union
  • c. International Telecommunications Union
  • d. International Telecommunications Units

ANS: C

15. The ITU is under the auspices of:

  • a. CCITT
  • b. the U.N.
  • c. IEEE
  • d. ANSI

ANS: B

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

ANS: B

17. The bits sent to allow equalization are called:

  • a. Gaussian bits
  • b. random bits
  • c. a training sequence
  • d. a random sequence

ANS: C

18. The V.90 standard is issued by:

  • a. the EIA
  • b. the TIA
  • c. the ITU
  • d. the ISO

ANS: C

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

ANS: B

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

ANS: A

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

ANS: C

22. The official name for RS-232C is:

  • a. RS-232C
  • b. EIA-232D
  • c. ISO-232C/D
  • d. ANSI-232C

ANS: B

23. In RS-232, a modem would be:

  • a. a DTR
  • b. a DSR
  • c. a DCE
  • d. a DTE

ANS: C

24. In RS-232, a personal computer would be:

  • a. a DTR
  • b. a DSR
  • c. a DCE
  • d. a DTE

ANS: D

25. On a DB-9 RS-232 connector, signal ground is pin:

  • a. 1
  • b. 3
  • c. 5
  • d. 7

ANS: C

26. On a DB-25 RS-232 connector, signal ground is pin:

  • a. 1
  • b. 3
  • c. 5
  • d. 7

ANS: D

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

ANS: B

28. Hardware flow control uses:

  • a. XON and XOFF
  • b. TD and RD
  • c. RTS and CTS
  • d. DSR and DCD

ANS: C

29. Software flow control uses:

  • a. XON and XOFF
  • b. TD and RD
  • c. RTS and CTS
  • d. DSR and DCD

ANS: A

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

ANS: D

31. DSL stands for:

  • a. Data Signal Line
  • b. Digital Signal Line
  • c. Digital Subscriber Line
  • d. Double-Speed Loop

ANS: C

32. ADSL stands for:

  • a. Asynchronous DSL
  • b. Asymmetrical DSL
  • c. Analog DSL
  • d. All DSL

ANS: B

33. In a CATV system, HFC stands for:

  • a. Head Frequency Control
  • b. Hybrid Frequency Control
  • c. Hybrid Fiber-Coax
  • d. Hybrid Fiber Control

ANS: C

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

ANS: A

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

ANS: C

COMPLETION

1. RTS means Request To ____________________.

ANS: Send

2. The response to RTS is ____________________.

ANS: CTS

3. FSK stands for Frequency-Shift ____________________.

ANS: Keying

4. DSR stands for ____________________ Set Ready.

ANS: Data

5. QAM stands for ____________________ Amplitude Modulation.

ANS: Quadrature

6. The number of symbols per second is called the ____________________ rate.

ANS: baud

7. The 2 bits of information in a QPSK symbol is called a ____________________.

ANS: dibit

8. QPSK uses ____________________ different phase angles.

ANS: four

9. DPSK stands for ____________________ PSK.

ANS: Delta

10. The QAM amplitude-phase combinations are shown with a ____________________ diagram.

ANS: constellation

11. ITU stands for International _________________________ Union.

ANS: Telecommunications

12. In QAM modems, ____________________ coding adds extra bits to improve performance on a noisy line.

ANS: Trellis

13. ____________________ is used in a high-speed modem to compensate for uneven frequency and phase response on a line.

ANS: Equalization

14. The maximum allowed speed for a modem on a dial-up line is about ____________________ bps.

ANS: 54k

15. The nominal maximum speed on an RS-232 cable is ____________________ bps.

ANS: 20k

16. In RS-232, the ____________________ line is asserted when the analog carrier from another modem is being received.

ANS:

CD

DCD

RLSD

17. Between hardware flow control and software flow control, ____________________ flow control is preferred.

ANS: hardware

18. A voltage higher than ____________________ volts should be considered a high on an RS-232 receiver.

ANS: 3

19. A ____________________ modem cable is used to connect two DTEs via their serial ports.

ANS: null

20. ADSL stands for ____________________ DSL.

ANS: Asymmetrical

21. A typical CATV system is organized as a ____________________ network.

ANS: tree

22. In a CATV system using cable modems, a ____________________ is used to put several channels of data onto a fiber-optic backbone.

ANS: CMTS

23. ____________________ is the process of synchronizing transmitted data from cable modems to a CMTS.

ANS: Ranging

24. ____________________ systems send high-speed data over a POTS line while sharing the line with dialup service.

ANS: ADSL

25. The ____________________ version of ADSL does not require a splitter at the subscriber end.

ANS: lite

26. ____________________ modulation divides the line bandwidth into many narrow bands called tones or bins for ADSL.

ANS: DMT

27. A DSLAM is a DSL Access ____________________.

ANS: Multiplexer

SHORT ANSWER

1. Calculate the bits per second capacity of a system sending 1000 symbols per second with 16 possible states per symbol.

ANS:

4000

2. How many points will be on the constellation diagram of a QAM system using 8 phase angles and 2 amplitude levels?

ANS:

16

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?

ANS:

720 kbps

4. A DMT system uses 4.3-kHz bins on a 1-MHz cable. Approximately how many bins are there?

ANS:

230

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?

ANS:

8

Complete List of MCQs in Electronic Communication Systems by Blake

Blake: MCQ in Digital Modulation and Modems
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