1. …………….. is the process of converting binary data, a sequence of bits to a digital signal.
A) Liners coding
B) Line coding
C) Digital coding
D) Binary coding
2. Which of the following is/are the characteristics of line coding.
i) signal level and data level ii) DC component iii) Pulse rate and bit rate iv) self-synchronization
A) i, ii and iii only
B) ii, iii and iv only
C) i, iii and iv only
D) All i, ii, iii and iv
3. Which of the following is/are the categories of line codes
i) Unipolar codes ii) Non polar codes iii) Bipolar codes iv) Polar codes
A) i, ii and iii only
B) ii, iii and iv only
C) i, iii and iv only
D) All i, ii, iii and iv
4. …………… have only one voltage level other than zero, so the encoded signal will have either +A volts value or 0.
A) Unipolar codes
B) Bipolar codes
C) Non polar codes
D) Polar codes
5. ………………… uses two voltage levels other than zero such as +A/2 and -A/2 volts.
A) Unipolar codes
B) Bipolar codes
C) Non polar codes
D) Polar codes
6. In ………………… format, a logic 1 is represented by a pulse of full bit duration Tb and amplitude +A while a logic 0 is represented by an off pulse or zero amplitude.
A) Unipolar RZ
B) Unipolar NRZ
C) Polar RZ
D) Polar NRZ
7. ………………. format shows that opposite polarity pulses of amplitude +-A/2 are used to represent logic 1 and 0. .
A) Unipolar RZ
B) Unipolar NRZ
C) Polar RZ
D) Polar NRZ
8. In ………………. format, the successive 1s are represented by pulses with alternating polarity and no pulse is transmitted for a logic 0.
A) Unipolar RZ
B) Unipolar NRZ
C) Bipolar NRZ
D) Polar NRZ
9. An attractive feature of the ………….. the absence of a dc component even through the input binary data may contain long string of 0s and 1s.
A) Bipolar format
B) Unipolar format
C) Split Phase Manchester format
D) Polar format
10. In ………………. format, symbol 1 is represented by transmitting a positive pulse of +A/2 amplitude for one half of the symbol duration, followed by a negative pulse of amplitude -A/2 for remaining half of the symbol duration.
A) Bipolar
B) Unipolar
C) Split Phase Manchester
D) Polar
11. Which of the following is/are the basic types of modulation techniques for transmission of digital signals.
i) Amplitude Shift Keying(ASK) ii) Frequency Shift Keying(FSK) iii) Phase Shift Keying(PSK)
A) i and ii only
B) ii and iii only
C) i and iii only
D) All i, ii and iii
12. ……………….. is a multilevel modulation in which four phase shift are used for representing four different symbols.
A) ASK
B) FSK
C) PSK
D) QPSK
13. The disadvantage of ………….. is that it is very sensitive to noise, therefore it finds limited application in data transmission.
A) ASK
B) FSK
C) PSK
D) QPSK
14. ………………. is the simplest type of digital CW modulation where the carrier is sinewave of frequency fc.
A) ASK
B) FSK
C) PSK
D) QPSK
15. State the following statements are True or False for the advantage of FSK.
i) FSK is relatively easy to implement
ii) It has better noise immunity than ASK.
iii) It increases the channel bandwidth required to transmit the FSK signal.
A) i-False, ii-True, iii-False
B) i-True, ii-True, iii-False
C) i-True, ii-False, iii-False
D) i-True, ii-True, iii-True
16. The …………………. is not preferred for the high speed modems since with increase in speed, the bit rate increases.
A) ASK
B) FSK
C) PSK
D) QPSK
17. ………………… is used for high bit rates, where the phase of the sinusoidal carrier is changed according to the data bit to be transmitted.
A) ASK
B) FSK
C) PSK
D) QPSK
18. …………………. has the best performance of all the systems in presence of noise, which gives the minimum possibility of error.
A) QPSK
B) BPSK
C) QAM
D) FSK
19. Which of the following is/are the advantages of BPSK.
i) BPSK has a bandwidth which is lower than that of the BPSK signal.
ii) BPSK is relatively easy to implement
iii) BPSK has a very good noise immunity.
A) i and ii only
B) ii and iii only
C) i and iii only
D) All i, ii and iii
20. As the telephone lines have a very low bandwidth, it is not possible to satisfy the bandwidth requirement of …………………… at higher speed.
A) ASK
B) PSK
C) FSK
D) QPSK
Answers
1. B) Line coding
2. D) All i, ii, iii and iv
3. C) i, iii and iv only
4. A) Unipolar codes
5. D) Polar codes
6. B) Unipolar NRZ
7. C) Polar RZ
8. C) Bipolar NRZ
9. A) bipolar format
10. C) Split Phase Manchester
11. D) All i, ii and iii
12. D) QPSK
13. A) ASK
14. A) ASK
15. B) i-True, ii-True, iii-False
16. B) FSK
17. C) PSK
18. B) BPSK
19. C) i and iii only
20. C) FSK
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