253. Retrace of electron beam is
A.(c) very slow
B. as fast as the trace
C. very fast
D. none of these

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254. In a television system, one frame contains 525 lines and vertical scanning frequency is 60 Hz. In such a case, the trace period is
A. 64 is
B. 52 is
C. 63.5 pis
D. none of these

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255. During field-blanking pulse width
A. 44 lines are blanked
B. 21 lines are blanked
C. 11-20 lines are blanked
D. none of these

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256.  According to NTSC standards, field sync occurs after
A. 525th line is scanned
B. half of 263rd line is scanned
C. lines 262 ?2 and 525
D. lines 312 ? and 625

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257.  The purpose of dividing each frame into two fields so as to transmit 50 views of picture per second (in CCIR standards) is
A. to avoid flicker in the picture
B. the fact that handling of higher frequencies is easier
C. that 50 Hz is power line frequency in India
D.both A and C

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258. In a 525 line system, if the vertical scanning frequency is increased, then
A. the spot may scan less number of lines per frame
B. the spot may scan number of lines greater than 525
C. we may get a vertical line on screen
D. none of these

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259. In a television camera, a picture element is located at a distance 1/2" from left and 1/5" from top of scanned area (1" x 3/4"). Same picture element when reproduced on television screen (20" x 15") will be positioned at
A. 10" from right and 3" from top
B. 1/2" from left and 1/5" from top
C. 1/2" from right and 1/5" from bottom
D. none of these

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