JNTU B.Tech II Semester Examinations, TELECOMMUNICATION SWITCHING SYSTEMS AND NETWORKS, Apr/May 2008

JNTU B.Tech II Semester Examinations, TELECOMMUNICATION SWITCHING SYSTEMS AND NETWORKS, Apr/May 2008

( Common to Electronics & Communication Engineering and Electronics &

Telematics)

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

SET-I

1. (a) Why is it necessary to keep the magnetic diaphragm in an earphone displaced

from its unstressed position? How is this achieved?

(b) What happens if the ratio ?/?0 is not very small in case of an earphone?

(c) Estimate the bandwidth requirements of a single satellite that is to support 20 million telephone conversations simultaneously. [8+4+4]

 

2. (a) Explain the operation of input controlled and output controlled time division

space switch with the help neat sketches?

(b) A PABX is designed using an output-controlled digital time division space switch for supporting 128 subscribers. The transmission between the subscribers and the exchange is analog. On an average, 25 % of the subscribers are active simultaneously, compare the cost of output- controlled and memory-controlled configurations. [8+8]

 

3. (a) A subscriber loop of 18km is to be supported from an exchange that uses a 40 V battery with a 400  short-circuit protection resistance. Electronic telephones are used as the subscriber instruments. Determine the wire gauge that needs to be used.

(b) Explain in detail about telecommunication network topologies? [8+8]

 

4. (a) Define grade of service? Give expression for grade of service and explain why

it is called as call congestion.

(b) The traffic statistics of a company using a PABX indicates that 180 out-going calls are initiated every hour during working hours. Equal number of calls comes in. Each call lasts for 200 seconds on the average . If the GOS required is 0.05, determine the number of lines required between the PABX and the main exchange. [8+8]

 

5. (a) Describe data communication circuit configurations.

(b) What are the components of Data Communication network ? Explain. [8+8]

 

6. (a) Define open system interconnection. Name and explain functions of each of

the Layers of the OSI model.

(b) Describe the operation of star, bus ring and hybrid Network topologies [8+8]

 

7. (a) What are the data link protocols used by ISDN ? Explain.

(b) Describe the four categories of messages in the ISDN network layer [8+8]

 

8. (a) Explain the format of STS 1 frame in details.

(b) What are the functions of STS- Multiplexes and add / drop multiplexers.

(c) Explain device layer relationship in SONET [6+6+4]

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