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From: whos@ddsw1.MCS.COM (Ben Feen)
Newsgroups: sci.electronics
Subject: Re: touch screen for crt display?
Message-ID: <1991May18.025326.375@ddsw1.MCS.COM>
Date: 18 May 91 02:53:26 GMT
References: <1656@fs1.ee.ubc.ca>
Organization: ddsw1.MCS.COM Contributor, Wheeling, IL
Lines: 30

In article <1656@fs1.ee.ubc.ca> jthornto@ee.ubc.ca (Johan Thornton) writes:
>Does anyone know either
>
>- where to get 
>- how to build
>
>a clear touch screen to fit over a monitor.  It doesn't have to have
>to have very high resolution--4 by 4 would be ok.
>
>One idea I had was to run some small wires across the screen and essentially
>use the classic capacitive touch-switch circuit.
>

Touch screens are not touch-operated, or at least the HP screens I've seen
aren't.  They are based on small transmitters and sensors around the
screen's border.  When you interrupt the beams crossing the screen, the
computer knows the X-Y  coord's of your finger.  The wires idea is cute, but
there are two problems:

1:  You'd have to prevent the "X" wires from shorting with the "Y" wires,
but still have them close enough to touch two at once.
2:  Who wants wires on their screen?

(BTW:  I THINK the above description of a touch screen is right.  If not,
feel free to correct me, but direct flames to dev/nul.
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