JNTU question papers 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) Explain about main design considerations for touch tone signaling?

(b) If the signal input to an amplifier is 0 dBm, what is the power output in Mw if the gain of the amplifier is 20dB.


2. (a) Compare centralized and distributed SPC?

(b) Determine the switch advantage ratio of a three-stage network with N inlets and N outlets for the cases when

i. N=128 and

ii. N=32,768.


3. (a) What are the factors that limit the length of subscriber loop? Explain.

(b) Determine the reference equivalent of a local call circuit, given the following

REs: For the telephone set, TRE = 3 dB, RRE = -3dB

For the subscriber line loop, TRE = 10 dB, RRE = 8 dB

For the exchange switch, RF = 1 dB.


4. (a) Define the following terms

i. Call completion rate

ii. Erlang

iii. Busy hour call attempts

iv. CCS.

(b) A group of 20 servers carry a traffic of 10 erlangs. If the average duration of a call is three minutes, Calculate the number of calls put through by a single server and the group as a whole in a one-hour period.


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. Draw the reference model used by Internet and explain the function of each layer.

What are protocols used by the model. Compare with OSI / ISO reference model.


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. (a) Compare ADSL, VDSL, HDSL and SDSL Technologies.

(b) What is CM & CMTS ? Explain.

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