From 1985 - HP 150 TouchScreen goes for >$400 !

[Stefan]

HP150 touchscreens work without touching. There are indeed rows on the top, 
bottom, left and right just in front the actual screen, if you break one of 
the "beams" it will detect that and do whatever its meant to do.

At 15:53 19-5-2005, you wrote:
> >>>>> "Tony" == Tony Duell <ard at p850ug1.demon.co.uk> writes:
>
>  >> I think I have the touchscreen frame from one of those, 4 circuit
>  >> boards linked together in a box, with a lots of LEDs and
>  >> phototransistors.  Always been curious what it came out of.
>
>  Tony> Quite possibly, that's how the touchscreen worked on the 150.
>
>Don't know about the 150, but that approach (rows and columns of light
>beams) is how the touch panels on PLATO terminals -- starting early in
>the 1970s -- worked.  Of course it's easier when the screen is flat,
>as it always has been for plasma displays.
>
>    paul

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