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Tlcm 122: Telecommunications Fundamentals I Question Paper
Tlcm 122: Telecommunications Fundamentals I
Course:Bachelor Of Telecommunication And Information Engineering ()
Institution: Kabarak University question papers
Exam Year:2011
KABARAK UNIVERSITY
UNIVERSITY EXAMINATIONS
2011/2012 ACADEMIC YEAR
FOR THE DEGREE OF BACHELOR OF TELECOMMUNICATIONS
TLCM 122: TELECOMMUNICATIONS FUNDAMENTALS I
DAY: WEDNESDAY DATE: 28/03/2012
TIME: 2.00 – 4.00 P.M. STREAM: Y2S1
INSTRUCTIONS:
1. Answer all the questions in part one and any two questions in part two
2. Any extra questions answered will not be marked
PART ONE
Question One (30 marks)
a. The diagram below is that of a simple telephone circuit.
i. Is the circuit simplex, half duplex or full duplex? Explain your answer. (3 marks)
ii. Explain the function of the inductor shown in the circuit. (3 marks)
b. Define circuit switching. (2 marks)
c. Explain what blocking means in circuit switching. (2 marks)
d. A multistage crossbar switch is designed using the following information
• Number of inlets = number of outlets = 2000
• Number of stages = 3
• Number of single stage crossbar switches in first stage = 20
• Number of single stage crossbar switches in second stage = 8
• Number of single stage crossbar switches in third stage = 25
Calculate the number of crosspoints in the multistage crossbar switch. (4 marks)
e. Using a diagram, describe how a TDM bus switch works. (4 marks)
f. Explain why a time slot interchanger (TSI) switch has a time delay associated with the
switching process. (2 marks)
g. With regard to a public switched telephone network (PSTN) exchange describe the
following connections
i. local connection (2 marks)
ii. Transit connection (2 marks)
h. The telephone number of a subscriber in PSTN consists of two parts.
i. Name and describe the meaning of each part. (3 marks)
ii. Explain how each part is used in the switching process. (3 marks)
PART TWO
Question Two (20 marks)
a. Describe one way that a transmission media modifies a signal transmitted on it, and name
a device that can be used to counter the effects of this modification. (2 marks)
b. Define the frequency spectrum of a signal. (2 marks)
c. Describe
i. Phase modulation (2 marks)
Page 3 of 4
ii. Frequency shift keying (2 marks)
d. 24 analog signals, each having frequency components between 200Hz and 2400Hz, are
frequency division multiplexed (FDM) using a guard band of 600Hz. The multiplexing
process uses amplitude modulation.
i. Determine the number of oscillators, modulators, demodulators and bandpass filters
required to for the frequency division multiplexing and demultiplexing processes.
(4 marks)
ii. What would be the consequence of not using guard bands in FDM? (2 marks)
iii. Calculate the minimum bandwidth required to transmit the FDM signal. (3 marks)
e. An active low pass filter has a maximum gain of 2450. Calculate the gain in decibels of
the filter at the cutoff frequency. (3 marks)
Question Three (20 marks)
a. Define digital transmission. (2 marks)
b. Encode the following binary data 10100101 using
i. Non return to zero code (2 marks)
ii. Manchester code (3 marks)
c. Between Manchester code and alternate mark inversion code, which code is self
synchronizing? Explain your answer. (3 marks)
d. An analog signal with frequency components between 2500Hz and 8000Hz is first
filtered using a low pass filter with a cut off frequency of 5600Hz. The filtered signal is
then digitized using pulse code modulation (PCM). The filtered signal is sampled at the
Nyquist rate. The quantization process uses 196 quantization levels.
i. Describe the pulse code modulation process. (3 marks)
ii. Define the quantization noise. (1 mark)
iii. State the Nyquist theorem (2 marks)
iv. Determine the bit rate of the resultant digital signal (4 marks)
Question Four (20 marks)
a. What are the B and D channels used for in integrated services digital network (ISDN) and
what are their bit rates? (3 marks)
b. Primary rate interface-integrated services digital network (PRI-ISDN) can be carried over
T1 or E1 carriers. Describe two differences between how PRI-ISDN is implemented over
E1 as compared its implementation over T1. (3 marks)
c. Describe in detail the formats of the T1 carrier system frame and the E1 carrier system
frame (6 marks)
d. 20 digital signals each with a bit rate of 6200bps are time division multiplexed (TDM).
The duration of each time slot is 4 milliseconds. Calculate the frame rate of the TDM
signal. (4 marks)
f. Give two advantages that standards bring to the telecommunications industry. (4 marks)
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