Maharashtra State Board of Technical Education 2007 Diploma Electronics and Communication Digital Communication - Question Paper

3 Hours / 100 Marks

Instructions - 1. All ques. are compulsory
2. ans every next main ques. on a new page.
3. Illustrate your answers with neat sketches wherever
necessary.
4. Figures to the right indicate full marks.
5. presume suitable data, if necessary.


1. Attempt any 5 of the following: MARKS:20

a) What are errors in DM? How to over come them? Draw block diagram
of the system for it.
b) Describe address structure of ISDN with diagram.
c) Describe base bank and pass band transmission.
d) Describe centralized SPC with block diagram.
e) Describe data transmission in PSTN with diagram.
f) Describe X.400 family if standards in ISDN.
g) Explain Hamming distance (dmin). How many errors can be corrected and detected for the provided minimum distance?

2. Attempt any 2 of the following: MARKS:16

a) Draw the sketch for packet switched network. discuss it working.
b) Explain the process of binary representation of a signal in PCM system with neat diagram.
c) With the help of block diagram and waveforms discuss generation of QAM.

3. Attempt any 2 of the following: MARKS:16

a) Draw and discuss the block diagram of CRC generator. provide 1 example.
b) What is common control? define common control switching system.
c) Describe different LAN topologies, with diagram. State their access methods.

4. Attempt any 4 of the following: MARKS:16

a) Define:
1) Folded network
2) Non folded network
3) Blocking n/w
4) Non blocking network.
b) Compare microprogrammed control with hard wired control.
c) Compare single stage network with multistage network.
d) Describe encoding procedure in PCM
e) Describe synchronous modem with block diagram.
f) State and discuss sampling theorem.

5. Attempt any 2 of the following: MARKS:16

a) With block diagram, define the operation of time multiplexed space switching.
b) Describe DPCM with block diagram. Compare it with PCM.
c) Describe FDMA transmission system with block diagram.

6. Attempt any 2 of the following: MARKS:16

a) Describe 3 stage network with diagram. Derive the formula for number of switching elements for blocking configuration.
b) Describe ISDN functional grouping and reference points, with diagram.
c) Describe the generation of BFSK with block diagram. State the mathematical formula. Draw power density spectrum.

Earning:   Approval pending.