 # Blake: MCQ in Digital Modulation and Modems

(Last Updated On: January 9, 2018)

This is the Multiple Choice Questions in Chapter 12: Digital Modulation and Modems from the book Electronic Communication Systems by Roy Blake . 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:

• 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

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

ANS: B

33. In a CATV system, HFC stands for:

• 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
• 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.

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.

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

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

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