[GreenKeys] Tape Facsimilie

[Harold Hallikainen]

On Mon, February 21, 2022 12:55 pm, Duncan Brown wrote:
> If you dig around that Hellschreiber site, you will find a section on
> Teletype Corp.'s Model 17.
> https://www.nonstopsystems.com/radio/hellschreiber-modes-other-mfrs-non-UK.htm#teletype-model-17
>
> Edward Kleinschmidt's original patent included a section on optical
> scanning of the message to be sent.  But Teletype Corp. settled on using
> a standard perforated 5-bit tape that was then fed into a machine that
> converted the 5-bit signal into the Hellschreiber signal.
>
> Have fun,
>
> Duncan
> K2OEQ

Thanks! I did not read far enough down the page. I really like the
simplicity of the printer in these systems. And optical scanning for the
transmit side is also simple. The Baudot to pixel converter is not a model
of simplicity! But sending at "tape speed" eliminates the problem of
figuring out when to stop the feed of tape at the printer end. I see that
they used 5x7 or 9x12 pixel patterns. I did a bunch of work with Unifont,
which uses 8x16 or 16x16 character bitmaps. That handles upper and lower
case characters plus an international character set of about 65,000
characters.

The knife edge pressing the paper against an inked wheel (a helix in the
Hellschreiber printer) is similar to the Bunnell pen recorder I worked on.

The various processes of applying ink to paper are fascinating!

Harold
https://w6iwi.org