MORE IN Digital Switching Systems
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Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1(a) Draw a neat diagram of four-wire circuit and explain its working.
10 M
1(b) A four wire circuit has an overall loss (two-wire to wire-wire) of 1 dB and the balance return loss at each end is 6 dB. Find: i) The singing point; ii) The stability margin; iii) The attenuation of talker and listener echo.
6 M
1(c) Write a short note on European pleisochronous digital hierarchy.
4 M

2(a) Differentiate between message switching and circuit switching.
4 M
2(b) Explain the functions of electronic swiching.
6 M
2(c) With the help of neat diagram, explain the basic types of calls that are usually processed through a DSS.
10 M

3(a) Derive the expression for second Erlang's distribution starting from basic principles.
10 M
3(b) Define the following terms:
i) Busy hour ii) Grade of service
iii) Pure chance traffic iv) Statistical equilibrium
4 M
3(c) On an average , one call arrives every 5 seconds. During a period of 10 seconds, what is the probability that :
i) No call arrives? ii) One call arrives?
iii) Two call arrive? iv) More than two calls arrive?
6 M

6 M
4(b) Derive the expression for grade of service of three stage network.
8 M
4(c) Design a three stage network for 100 incoming trunks and 400 outgoing trunks.
6 M

5(a) Explain S-T-S switching network with neat diagram.
6 M
5(b) A T-S-T network has 20 incoming and 20 outgoing PCM highway, each conveys 30 channels. The required GOS is 0.01, 0.02, 0.001, 0.005. Find the traffic capacity of network in mode 1 and mode 2.
8 M
5(c) Explain the need for frame alignment in time division switching network.
6 M

6(a) Explain iin brief basic software archiecture of a typical DSS with neat diagram.
10 M
6(b) With a neat diagram, explain digital switching system software classification.
10 M

7(a) Explain the organizational interfaces of typical DSS central office.
10 M
7(b) Explain with a neat diagram, a strategy for improving software quality.
10 M

Write short notes on:
8(a) Generic switch software architecture c. Common characteristics of DSS d. Analysis report for DSS
5 M
8(b) Recovery strategy
5 M
8(c) Common characteristics of DSS
5 M
8(d) Analysis report for DSS
5 M

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