NATIONAL OPEN UNIVERSITY OF NIGERIA
14/16 AHMADU BELLO WAY, VICTORIA ISLAND, LAGOS
SCHOOL OF SCIENCE AND TECHNOLOGY
MARCH/APRIL 2014 EXAMINATION
COURSE CODE: CIT 303
COURSE TITLE: PRINCIPLES OF COMMUNICATION TECHNOLOGY
TIME ALLOWED: 3HOURS
INSTRUCTION: ATTEMPT ANY FIVE (5) QUESTIONS
Question 1
a. Encrypt the word “IGNORANCE” with the following ciphers:
i. Shift cipher with key=1 (1 mark)
ii. Shift cipher with key= 26 (2 marks)
iii. Shift cipher with key=0 (2 marks)
iv. Transposition cipher where plain text: 1 2 3 4 5 6 7 8 9 and
cipher text: 4 3 1 5 2 6 7 9 8 (with no bogus character) (1.5 marks)
b. Decrypt the word “ANCEIGNOR” with the following ciphers:
i. Shift cipher with key=1 (1 mark)
ii. Shift cipher with key= 26 (2 marks)
iii. Shift cipher with key=0 (2 marks)
iv. Transposition cipher where plain text: 1 2 3 4 5 6 7 8 9 and
cipher text: 4 3 1 5 2 6 7 9 8 (with no bogus character) (1.5 marks)
c. The amplification in a cable is usually defined in decibels per kilometer (dB/km). If the signal at the beginning of a cable with 2 dB/km has a power of 2 mW, what is the power of the signal at 5 km? (3 marks)
d. Briefly explain the term attenuation (1.5 marks)
Question 2
.
a. Define the term “network topology”. (1 mark).
b. With the aid of diagrams, briefly explain the following network topologies:
i. Ring (3 marks)
ii. Mesh (3 marks)
iii. Tree (3 marks).
c. State and briefly explain 3 advantages and 3 disadvantages of using fiber optic cables in networking. (6 marks)
d. State 1 advantage and 2 disadvantages of STP cables in comparison to UTP cables. (1.5 marks)
Question 3
a. With the aid of a table ONLY, describe the five classes of IPv4 addresses under the following columns: (10 marks)
i. IP Address Class
ii. Format
iii. Purpose
iv. Number of network/ host bits
v. Max number of hosts
b. Briefly explain each of the following terms:
i. Linear filter (2 marks)
ii. Stable filter (1 mark)
iii. Unstable filter (1 mark)
iv. Time-invariant filter (1 mark)
v. Adaptive filter (1 mark)
vi. Linearity (in the context of linear-time invariant (LTI) (1.5 marks)
Question 4
i) Outline four (4) basic Network Topologies.
ii) List three guided Media.
iii) In one sentence, describe the OSI reference model (1 mark)
Question 5
a. Briefly explain the 3 modes of communication (with regards to the direction of communication). In each case, identify 2 examples of devices that utilize that mode of communication. (9 marks)
b. State the following:
i. 4 services/ functions provided by the OSI Physical Layer (2 marks)
ii. 4 services/ functions provided by the OSI Data Link Layer (2 marks)
iii. 4 services/ functions provided by the OSI Transport Layer (2 marks)
iv.3 services/ functions provided by the OSI Session Layer (2.5 marks)
Question 6
Contrast between:
i) Analog Signal Processing
ii) Digital Signal Processing
Question 7
a) What is Data Communications?
b) Define Protocols.
c) The effectiveness of a data communications system depends on four fundamental characteristics. List and define these characteristics.
You can get the soft copy for this course (2014-till date) at a little token or the exam summary answers for this course from 08039407882
Exam summary sample below
