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Posted by Richard Crowley on 06/25/07 18:36
"peter" wrote ...
> Is it generally true that countries with 60Hz AC outlet use NTSC and
> countries with 50Hz AC outlet use PAL?
Generally.
> Is it advantageous to have the vertical refresh rate be the same as or
> very close to the AC frequency?
It was advantageous to make the V rate and the line/mains frequency
identical to avoid moving hum-bars from various interference sources.
Alas, when the US NTSC standard for color was devised, they changed
the V rate to 59.97 Hz and we now have a hum-bar with ~10-second
period. Of course, under ideal conditions you never see any hum-bar.
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