Tuesday, December 8, 2009


Eighth Semester

(Regulation 2004)

Electronics and Communication Engineering


(Common to B.E. (Part – Time) Seventh Semester Regulation 2005)

Time: Three hours Maximum: 100 marks

Answer ALL questions.

PART A – (10 X 2 = 20 marks)

01)Compare synchronous and statistical time division multiplexing.

02)What is meant by data scrambling?

03)Define time division time switching.

04)Compare the cross point requirements for non blocking operation of three stage and single stage space division network when the number of lines is 8192.

05)What is meant by an elastic store?

06)Define timing jitter.

07)What are the functions of ISDN U interface?

08)Compare FTTH and FTTC.

09)A group of 20 servers carry traffic of 10 Erlangs. If the average duration of a call is two minutes, calculate the number of calls put through by a single server.

10)Define call congestion.

PART B – (5 X 16 = 80 marks)

11)(a)(i) Draw and explain time division multiplex loops and rings [Marks 8]

(ii) Give a brief note on Binary N zero substitution. [Marks 4]

(iii) State the advantages and disadvantages of partial response signaling. [Marks 4]


(b) (i) Explain the payload framing and frequency justification operations in SONET. [Marks 8] (ii) Draw and briefly discuss the different types of SONET rings [Marks 8]

12)(a) (i)Explain the operation and features of No.4 ESS toll switch with a neat diagram.[Marks 10] (ii) Discuss the operation of TST switch with a neat diagram [Marks 6]


(b) (i) Write about digital switching in analog environment [Marks 8] (ii) Discuss the operation and application of digital cross connect system. [Marks 8]

13)(a) (i) Discuss the main sources of clock instability in a digital network [Marks 6]

(ii) Discuss the principle of network control and management. [Marks 10]


(b) (i) Enumerate the different approaches of synchronizing digital networks [Marks 16]

14)(a) (i) Explain the techniques used in high data rate digital subscriber loops. [Marks 8]

(ii) Discuss the principles of digital loop carrier systems. [Marks 8]


(b) Write short notes on:

(i) Hybrid fiber coax systems. [Marks 6]

(ii) PCM modems. [Marks 6]

(iii) ISDN B and D channels. [Marks 4]

15)(a) (i) Explain the LCC systems with infinite sources and derive the Erlang B formula. What happens when the sources become finite? [Marks 10 + 2]

(ii) A rural telephone exchange normally experiences four call origination per minute. What is the probability that exactly seven calls occur in an arbitrarily chosen interval of 20 second [Marks 4]


(b) (i) Compare LCH and LCR systems. [Marks 6]

(ii) Discuss the applications of delay systems in modeling and analyzing communication networks. [Marks 10]

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