JNTU III B.Tech Supplimentary Examinations, Aug/Sep 2008

JNTU III B.Tech Supplimentary Examinations, Aug/Sep 2008


( Common to Electronics & Communication Engineering and Electronics &



1. (a) List all the event sequences that occur for call setup , call maintenance and call termination in a telephone exchange environment for

i. Local call

ii. Trunk call.

(b) Estimate the number of the cross points required to design an exchange that supports 500 users on a non blocking basis and 50 transit , outgoing or incoming calls simultaneously.


2. What are the different ways of controlling the time switch? Explain.


3. (a) What are the charges for telephone call of 1, 3 and 5 minute durations on BSNL telephone network, from warangal to kavali which are separated by a radial distance of 312 km. Determine these values for peak hours and off peak hours?

(b) A local loop has a resistance of 1 k and the telephone connected to it has an off hook resistance of 250 .Find the loop current and voltage when the phone is


ii. OFFHOOK. The CB voltage is 48V.


4. (a) Describe typical telephone traffic pattern on a working day?

(b) An exchange serves 2000 subscribers. If the average BHCA is 10,000 and the CCR is 60%, Calculate the busy hour calling rate.


5. (a) Explain point to point and Multipoint data communication circuit configurations.

(b) What are the merits and demerits of serial and parallel data transmission.

(c) Explain basic concepts of connection oriented and connectionless protocols.


6. (a) Explain the function of each layer of ISO OSI reference model with the help of neat sketch.

(b) What are the principles that were applied to arrive at different layers in OSI reference mode ? Explain.


7. (a) What are the objectives of ISDN ? Explain.

(b) Describe the conceptual view of ISDN and what is meant by the term digital pipe.

(c) Discuss ISDN system connections and Interface units.


8. Briefly explain

(a) STS-1 signal frame format.

(b) Automatic Protection Switching.

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