JNTU B.Tech II Semester Examinations, TELECOMMUNICATION SWITCHING SYSTEMS AND NETWORKS, Apr/May 2008
( Common to Electronics & Communication Engineering and Electronics &
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
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]