William Sommerwerck wrote:
Well, the story I heard way back when is that it was to synchronise
the picture's vertical frequency with the mains frequency, so that
inadequacies in power smoothing produced static distortions in the
picture rather than much more noticable rolling distortions.

That's what I heard, too. But that's not "interefence effects from
electrical lights".

You are assuming that all interference would be on the screen itself and none
would be visual. Since flourescent and to some extent incandescent lights
blink (what is the persistance of an incadescent light?) at 60 Hz, there is
a strobing effect if there are lights on in the room with the TV.

While some peope (me) like to watch TV in the dark, many people watch TV's
with lights on. Some manufacturers went as far as to include light sensors
in their TV sets automaticly adjusting the brightness to compensate for
room lighting as it changes.

Since some people live in places where only flourescent lights are allowed,
they have no choice if there is interference, either turn off the lights
entirely, or live with it.

I guess that could be a new tourism slogan for this summer, "Visit Israel,
and bring home real light bulbs." :-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.