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G.C.E. Advanced Level – 2020 (Paper Class)

INFORMATION COMMUNICATION TECHNOLOGY

Tutorial 16 (Dec 3)

ish,qu m%YaK j,g ms<s;=re imhkak'

1. Read the following statements from question 1 to 10 and mark "True" if correct or mark "False" if incorrect. my; oelafjk m%ldY i;H o wi;H o hkak kï lrkak'

i. When digital signal get mixed up with noise we cannot separate the signal and noise.

ixLHdxl ix× iu. f>daIdj tla jQ úg wmg ix×j iy f>daIdj fjka l< fkdyel'

ii. If a noise affected, analog signal is amplified signal and noise both will be amplified.

m%;siu ix× iu. f>daIdj tla jQ úg" wm tu ix×j j¾Okh l<fyd;a f>daIdj o j¾Okh fõ'

iii. bits per second is unit of measurement for digital bandwidth

;;amrhg ìÜ hkak ixLHdxl j, nEkaâ ú;a uksk tallhhs'

iv. Pulse code modulation is a method to convert an analog signal into a digital signal. lïmk fla; uQ¾cKh hkq m%;siu ix× ixLHdxl njg m;a lrk l%uhls'

v. In analog modulation both modulating signal (data input) and modulated signal (output

signal) are in analog format.

m%;siu uQ¾cKfha§ uQ¾cKhg ,la lrk ix×j iy uQ¾ð; ix×j hk folu m%;siu ;;ajfha mj;S'

vi. If S/N is high, quality of the signal also high.

ix×j$ f>daIdj w;r wkqmd;h jeä kï ix×fõ ;;ajh o jeäh'

vii. If an analog signal travels long distance, noise can be mixed. Clock signal can be used to

regenerate the original analog signal.

m%;siu ix× b;d ÿr iïfm%aIKh lsÍfï§ thg f>daIdj tla úh yel' miqj tu f>daIdj tla jQ ix×jg laf,dla ix× ,nd §fuka kej; uq,a m%;siu ix×j u ,nd.; yel'

viii. In an amplitude modulation process, the frequency of the carrier signal can be change

according to the amplitude of useful (data) signal.

úia;dr uq¾cKfha§ jdyl ;rx.fha ixLHd;h o m%fhdackj;a ;rx.fha úia;drhg wkqj fjkia úh yel'

ix. Multiplexing is a method which can send many signals in a single pair of cables without any

mixing.

nyqm:lrKh hkq fndfyda ix× tlu /yeka hq.,hla ;=, lsisÿ ñY% ùulska f;drj tlg iïfm%aIKh l< yels l%uhls'

x. Interference is not affected to the radio transmission.

f¾äfhda ;rx. iïfm%aYKhg ksfrdaOkh isÿ fkdfõ'

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2. List two main problems which limit the bandwidth in the following transmission media.

my; i`oyka udOH j, ix× iusfm%aIKfhaoS ;rx.fha bandwidth iSudlrk wjdis 2 ne.ska kus lrkak'

Copper Cables Fiber optics Radio signal

3. Compare two aspects of Twisted Pair cables and Fiber Optics in data communication.

my; i`oyka udOHhka ys o;a; iïfm%aKfha oelsh yels ,laIK 2 ne.ska kï lrkak'

Twisted Pair Fiber Optics

4. What are the 5 main requirements to be satisfied to a data communication?

o;a; ikaksfõokhla isÿlsÍu i`oyd ;sìh hq;= uQ,sl wjYH;d 5 kï lrkak'

5. Write 2 characteristics of a Digital Signal and 3 characteristics of an Analog signal.

ixLHdxl ;rx. j, ,dlaIKsl 2 la iy m%;siu ;rx. j, ,dlaIKsl 3 la ne.ska i`oyka lrkak'

6. Modulation is one of technique used to transmit signals & data.

uQ¾cKh hkq o;a; iy ix× iïfm%aIKh i`oyd fhdod.kakd ;dlaIKhls

i. uQ¾cKh hkq l=ulao@

ii. uQ¾ckh lsÍug isÿjk wjia:d 2 la kï lrkak

iii. m%;siu uQ¾ckh hkq l=ulaoehs y`ÿkajd m%;siu uQ¾cK l%u 3 la kï lrkak'

iv. ixLHdxl uQ¾ckh hkq l=ulaoehs y`ÿkajd ixLHdxl uQ¾cK l%u 3 la kï lrkak'

v. my; i`oyka uQrack jra. fudkjdoehs kus lrkak'

(a) .......................... (b) ..................................

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7.

i. What are the 4 main types of Phase differences? (Draw) ix× uq¾cKfha§ fhdod .kakd m%Odk l,d fjkialï 4 kï lrkak'

ii. Draw digital modulated signals for the following bit pattern. (For each 3 types) my; oelafjk ìÜ rgdj i`oyd l%u 3 gu wod, ixLHdxl uq¾cK ;rx.h we`o olajkak'

iii. What is Carrier signal and what are the characteristics of them? jdyl ;rx.hla hkq l=ulao@ jdyl ;rx.hl uQ,sl ,dlaIKsl fudkjdo@

8.

i. Why do we need digital encoding for digital data? (Give 2 examples)

wmg o;a; ixLHdxl ix× njg m;alsÍug wjYH jkafka wehs@ WodyrK 2 la i`oyka lrkak'

ii. Following bit patterns are represented some portion of digital data. Draw the encoding

patterns according to each technique.

my; oelafjk ìÜ rgdj ixLHdxl fla; ix×lrkhg wod, uQ,sl Wml%u 5 g wkqj

fla;kh lrkak'

0 1 1 0 0 1 1 1 0 0 0 1 0 1 0

Bipolar-AMI

NRZ-L

NRZ-I

Manchester

Differential

Manchester

0 0 1 0 1 1 1 0 0 1 0

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9.

i. nyqm:lrKh hkq l=ulao@

ii. nyqm:lrKfha jdishla iy wjdishla ne.ska kï lrkak'

iii. uQ,sl nyqm:lrKh ;dlaIKsl l%u fudkjdo@

iv. nyqm:lrKh hk ;dlaIKsl l%uh Ndú;hg .efkk m%dfhda.sl wjia:d 2 la kï

lrkak'

10.

a) Assume, that you need to store 5 minutes song on a Compact Disk by using Pulse Code

Modulation. Sampling rate is 7200 samples per second and number of quantization levels are

1024. Tng ñks;a;= 5 l muK ld,hla jk .S;hla lïmk fla; uq¾cKh u.ska ixhqla; ;eáhl .nvd lsÍug we;ehs is;kak' fuys§ Tn fhdod .kakd uDÿldx.h u.ska ;;amrhg idïm, 7200 la muK idïm,alrKhla mj;ajd .kakd w;r tla idïm,hla uÜgï 1024 lg uÜgï lrhs'

i. What is the output bit rate of the song?

by; § ,nd .kakd m%;sodkfha bit rate fidhkak'

ii. What will be the space required in a CD to record the song?

tu .S;h ixhqla; ;eáhl .nvd lrkafka kï ta i`oyd hk bv m%udKh wdikak jYfhka fldmuKoe hs .Kkh lrkak'

b) Consider sending a baseband audio signal, with bandwidth of 30 kHz, by pulse-code

modulation (uniform quantization). The highest value of quantization is 512 and the no of

samples in one second is 10000 samples.

lsf,da y¾Üia 30 l muK ixLHd;fhka hq;a Yío ;rx.hla lïmk fla; uq¾cKh u.ska iïfm%aIKh lrhs' tys§ fhdod .kakd Wmßu uÜgu 512 jk w;r ;;amrhla i`oyd idïm, 10000 la ,nd .kS'

i. Find the bit rate.

by; § ,nd .kakd m%;sodkfha bit rate fidhkak'

ii. Suggest 2 methods to increase the quality of the signal in order to PCM.

lïmk fla; uq¾cKh u.ska ,nd .kakd m%;sodkfha ;;ajh (quality) jeä lr .ekSu i`oyd isÿ l< yels Wml%u 2 la fhdackd lrkak'

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