From: utzoo!decvax!microsof!uw-beave!jim
Newsgroups: net.video
Title: Re: Monitor as well as television?
Article-I.D.: uw-beave.276
Posted: Wed Jan  5 10:26:53 1983
Received: Thu Jan  6 05:26:09 1983
References: ihuxm.145

The big problem is that most modern TVs use a hot chassis.  This means
that chassis ground, which is one of the two wires going into the
baseband video circuit, is connected to one side of the AC line.  This
is considered a shock hazard.  The RF modulator is a kind of AC
isolator.

For VCRs I don't think the RF modulator limits you very much because
the signal coming out of the VCR is so poor (please no flames).  But
for video games and home computers this a big loss.  It has even
convinced some computer manufacturers to limit their screens to 40
characters wide, or less.  The ironic part is that an RF modulator is a
whole lot more expensive than the better alternative, opto-isolators.
An RF modulator is about $50, an opto-isolator is more like $5.  An
opto-isolator has more bandwidth than any monitor.  The problem is that
it would have to be built in to the TV, and would add a whole $5 or so
to the manufacturer's cost.  The RF modulator doesn't cost the TV
manufacturer anything (but it does cost you $50).

I keep hoping that the new FCC rules about TV interference will make RF
modulators so expensive that there will be pressure on the TV makers to
put opto-isolators in their TVs and provide baseband video inputs, but
so far I've seen no evidence of this.