Subject Name: Data Communications
Subject Code: CS 501
QUESTION BANK - THEORY
UNIT-I
1. What is the relationship between period and frequency?
2. What does the amplitude of a signal measure? What does the frequency of a
signal measure? What does the phase of a signal measure?
3. How can a composite signal be decomposed into its individual frequencies?
4. Name three types of transmission impairment.
5. Distinguish between baseband transmission and broadband transmission.
6. Distinguish between a low-pass channel and a band-pass channel.
7. What does the Nyquist theorem have to do with communications?
8. What does the Shannon capacity have to do with communications?
9. Why do optical signals used in fiber optic cables have a very short wave length?
10. Can we say if a signal is periodic or non-periodic by just looking at its frequency
domain plot? How?
11. Is the frequency domain plot of a voice signal discrete or continuous?
12. Is the frequency domain plot of an alarm system discrete or continuous?
13. We send a voice signal from a microphone to a recorder. Is this baseband or
broadband transmission?
14. We send a digital signal from one station on a LAN to another station. Is this
baseband or broadband transmission?
15. We modulate several voice signals and send them through the air. Is this
baseband or broadband transmission?
16. Given the frequencies listed below, calculate the corresponding periods.
a. 24Hz
b. 8 MHz
c. 140 KHz
17. Given the following periods, calculate the corresponding frequencies.
a. 5 s
b. 12 ms
c. 220 ns
18. What is the phase shift for the following?
a. A sine wave with the maximum amplitude at time zero.
b. A sine wave with maximum amplitude after 1/4 cycle.
c. A sine wave with zero amplitude after 3/4 cycle and increasing.
19. What is the bandwidth of a signal that can be decomposed into five sine waves
with frequencies at 0, 20, 50, 100, and 200 Hz? All peak amplitudes are the
same. Draw the bandwidth.
20. A periodic composite signal with a bandwidth of 2000 Hz is composed of two
sine waves. The first one has a frequency of 100 Hz with maximum amplitude of
20 V; the second one has maximum amplitude of 5 V. Draw the bandwidth.
21. Which signal has a wider bandwidth, a sine wave with a frequency of 100 Hz or
a sine wave with a frequency of 200 Hz?
22. What is the bit rate for each of the following signals?
a. A signal in which 1 bit lasts 0.001 s.
b. A signal in which 1 bit lasts 2 ms.
c. A signal in which 10 bits last 20 J-ls
23. A device is sending out data at the rate of 1000 bps.
a. How long does it take to send out 10 bits?
b. How long does it take to send out a single character (8 bits)?
Chameli Devi Group of Institutions
Department of Computer Science and Engineering
