13 Oct
2015
13 Oct
'15
11:02 p.m.
Do you remember Carrol Touch terminals made in the area? I just picked up 2
still in the box!
On Tue, Oct 13, 2015 at 1:32 PM, Paul Koning <paulkoning at comcast.net> wrote:
On Oct 13, 2015, at 1:22 PM, tony duell <ard
at p850ug1.demon.co.uk> wrote:
The Versatec electrostatic plotters are not the same as the VT52
printer, they
are
yet another process. WIth those the paper passes
between a set of
electrodes that
build up a charge image on the paper. I beleive
the paper is specially
treated to
make it more resistive so the charge doesn't
leak away too quickly, and
there is
a clever multiplexing scheme for the electrodes
to reduce the number of
HV drivers
needed (IIRC there is around 600V between the
electrodes on the 2 sides
of the
paper.
The paper then passes over a stream of liquid toner, which is attracted
to the
charge
image. The liquid evaporates leaving the toner on
the paper. That's it,
no further
processing.
Speaking of Versatec: at University of Illinois, there was a PLATO
terminal that had a "Versatec screen printer". I never understood how that
worked. It smelled like the same electrostatic liquid toner technology.
But how the image got from the terminal to the printer is unclear.
Remember that these were plasma panel displays, where the graphics state
exists only inside the gas pixels in the panel. I wonder if they read out
the on/off state of the pixels somehow, but how to do that when there's a
100 volt or so square wave voltage across the panel is not obvious. I have
never seen any documentation of this machine.
paul