> On Feb 17, 2025, at 2:58 PM, Van Snyder <van.sny...@sbcglobal.net> wrote:
>
> On Mon, 2025-02-17 at 08:53 -0500, Paul Koning wrote:
>>
>>
>>
>>
>>> On Feb 16, 2025, at 7:38 PM, Van Snyder via cctalk <cctalk@classiccmp.org>
>>> wrote:
>>>
>>> .... It also
>>> had a thermal printer called "teledotis." It was very fast, so some
>>> called it the Whippet. It electrostatically deposited soot onto special
>>> paper, which was then fused by a heat roller.
>>
>> I would call that an "electrostatic printer" -- xerographic printer work
>> that way, depositing plastic soot that is then melted onto the paper. At U
>> of Illinois I used a printer very much like what you describe, made by
>> Varian. That was a dot matrix line printer -- a row of pixels across the
>> page at once -- we used for printing music scores. 100 dpi or so if I
>> remember right.
>
>
> One of my university classmates worked for American Geophysical. They would
> lay out a few thousand feet of cables with "geophones" on them, then drive
> around with "thumper" trucks. They analyzed the data using Varian V70
> computers with FFT in microcode. They printed the resulting maps on 36" wide
> scrolls using — you guessed it — Varian electrostatic printers.
> ...
> The Varian brothers were true geniuses.
Indeed. There's a wonderful photo of them by Ansel Adams. Look for it; it
shows the two of them doing a mad-genius imitation, with a random collection of
waveguides and the like in their hands.
The Varian printer had one interesting issue. It had a chain drive, with some
slack in the chain. If you fed it data non-stop it worked great, but if you
ever had to pause the data stream, the stop and start of the paper would leave
a gap in the output. Very visible if you were trying to plot continuous lines
(like the 5 horizontal lines in a music score). The original application to
feed that printer on the PLATO system was a batch job that routinely got
pre-empted by the scheduler, just long enough for its buffer to go empty. I
ended up doing the whole job in PPUs (reading the input file as well as feeding
the printer).
paul
