# Blake: MCQ in Digital Modulation and Modems

(Last Updated On: January 3, 2020) 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

Solution:

2. PSK stands for:

a. Pulse-Signal Keying

b. Pulse-Shift Keying

c. Phase-Signal Keying

d. Phase-Shift Keying

Solution:

3. QAM stands for:

d. none of the above

Solution:

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

a. amperes

b. amperes per second

c. bits

d. bits per second

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

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

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

Solution:

8. High-frequency radioteletype systems commonly use:

a. FSK

b. AFSK

c. PSK

d. QAM

Solution:

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

a. a byte

b. 4 bits

c. a dibit

d. a Q-bit

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

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

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

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

Solution:

14. ITU is an abbreviation for:

a. International Telephony Unit

b. International Telephony Union

c. International Telecommunications Union

d. International Telecommunications Units

Solution:

15. The ITU is under the auspices of:

a. CCITT

b. the U.N.

c. IEEE

d. ANSI

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

Solution:

17. The bits sent to allow equalization are called:

a. Gaussian bits

b. random bits

c. a training sequence

d. a random sequence

Solution:

18. The V.90 standard is issued by:

a. the EIA

b. the TIA

c. the ITU

d. the ISO

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

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

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

Solution:

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

a. RS-232C

b. EIA-232D

c. ISO-232C/D

d. ANSI-232C

Solution:

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

a. a DTR

b. a DSR

c. a DCE

d. a DTE

Solution:

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

a. a DTR

b. a DSR

c. a DCE

d. a DTE

Solution:

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

a. 1

b. 3

c. 5

d. 7

Solution:

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

a. 1

b. 3

c. 5

d. 7

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

Solution:

28. Hardware flow control uses:

a. XON and XOFF

b. TD and RD

c. RTS and CTS

d. DSR and DCD

Solution:

29. Software flow control uses:

a. XON and XOFF

b. TD and RD

c. RTS and CTS

d. DSR and DCD

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

Solution:

31. DSL stands for:

a. Data Signal Line

b. Digital Signal Line

c. Digital Subscriber Line

d. Double-Speed Loop

Solution:

a. Asynchronous DSL

b. Asymmetrical DSL

c. Analog DSL

d. All DSL

Solution:

33. In a CATV system, HFC stands for:

b. Hybrid Frequency Control

c. Hybrid Fiber-Coax

d. Hybrid Fiber Control

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

Solution:

35. A “splitter” at the subscriber end is not required for:

a. Any DSL scheme

d. none of the above

Solution:

COMPLETION

1. RTS means Request To ____________________.

Solution:

2. The response to RTS is ____________________.

Solution:

3. FSK stands for Frequency-Shift ____________________.

Solution:

4. DSR stands for ____________________ Set Ready.

Solution:

5. QAM stands for ____________________ Amplitude Modulation.

Solution:

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

Solution:

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

Solution:

8. QPSK uses ____________________ different phase angles.

Solution:

9. DPSK stands for ____________________ PSK.

Solution:

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

Solution:

11. ITU stands for International _________________________ Union.

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

CD

DCD

RLSD

Solution:

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

Solution:

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

Solution:

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

Solution:

20. ADSL stands for ____________________ DSL.

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

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

Solution:

27. A DSLAM is a DSL Access ____________________.

Solution:

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

Solution:

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

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?

Solution:

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

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?

Solution:

### Complete List of MCQ in Electronic Communication Systems by Blake

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