Xref: utzoo sci.electronics:17971 sci.energy:4042
Newsgroups: sci.electronics,sci.energy
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: VDT Electric Fields
Message-ID: <1991Feb22.174257.19533@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <12438@pucc.Princeton.EDU> <1991Feb13.002236.8087@sj.ate.slb.com> <1991Feb19.232959.28401@zoo.toronto.edu> <1991Feb21.183853.28327@sj.ate.slb.com>
Date: Fri, 22 Feb 1991 17:42:57 GMT

In article <1991Feb21.183853.28327@sj.ate.slb.com> jones@sjs.sj.ate.slb.com (Clark Jones) writes:
>>This in turn is a safety issue.  Keeping the 110VAC wiring in a tight little
>>clump at the back makes it substantially easier to pass safety standards...
>
>Henry, have you forggotten entirely about the rather dangerous voltages that
>these things require to work?

Of course not, but what difference does that make?  You're *still* safer if
the 110VAC is restricted to a small section.  It is, if anything, a bigger
hazard than the high voltages, since it can supply a whole lot more current.

>Furthermore, having to reach around to the back _DECREASES_ safety...

Perhaps.  Terminals do not ignite very often. :-)  You have to balance the
awkwardness of getting at the power switch when it's put at the back
against reduced hazards from physical abuse and manufacturing error when
high-power wiring is minimized.

You are also ignoring cost considerations; note the word "easier" in my
comments.  All the safety features in the world don't help if your boss
won't buy it because something else is cheaper.  People are seldom willing
to pay extra for arguably-better safety in very unlikely situations.

>But to really blow your argument out of the water, Henry, a quick check of
>the two monitors on my desk (a 19" color from Sun and a DEC VT-100) reveals
>that _neither_ of them make use of a third-party switch/fuse/plug/filter
>module...

I hate to point this out, but my argument still floats solidly. :-)  For
one thing, although you don't specify the make of Sun so I can't say about
it, the VT-100 design is 15 years old.  It actually took quite a while for
reasonably comprehensive modules to appear.  For another thing, you are 
talking about products built in huge volume by large manufacturers, who
are very conscious of the long-term merits of spending a little extra to
build custom solutions rather than using off-the-shelf parts that cost
five cents more each.

>No, it is not a safety issue, just plain anti-ergonomics.

Contrary to popular belief, manufacturers do not take sheer malevolent joy
in making equipment hard to use.  There are usually good reasons, or at
least reasons that are perceived as good, for these decisions.  Keeping
the AC power handling concentrated in one small area is a safety improvement,
at least by UL/CSA/etc rules.  Keeping it out of the equipment entirely is
a still bigger win, which is why lots of things now use external "brick"
power supplies (which let the power-supply manufacturer do all the worrying
about AC).
-- 
"Read the OSI protocol specifications?  | Henry Spencer @ U of Toronto Zoology
I can't even *lift* them!"              |  henry@zoo.toronto.edu  utzoo!henry


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