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| Public domain image courtesy Pexels. |
Remember
when you were young and could hear the high pitched whine of the
horizontal line scan transformer in a TV that was using the 625 line
system? The line output or LOPT transformer operated at 15,625 Hz, and
you could tell that the TV was turned on, even with the sound turned
down. Before that in the early 70s, vertical resolution was 405 lines.
Young children can hear up to a frequency of 20 kHz. Most of us over 50
can only hear to 10 kHz.
