[GreenKeys] Teletypes round 2

[Jim Haynes]

On Sun, 31 Mar 2019, Harold Hallikainen wrote:
>
> Speaking of model 20, my school newspaper had one with a tape punch. At

That must have been quite a school with a Linotype and all that kind of
stuff.

> Printing in general is quite interesting! Stuff like the Teletype model 15
> was definitely designed around a classic typewriter. Then there were daisy
> wheel printers (I had one of those!). And the IBM Selectric (to me,
> amazing mechanics!). Then impact dot matrix.

Teletype patented a daisy wheel printer in 1939  (patent 2,146,380) but
so far as I know never produced any.  In those days it had to work in the
same fashion as the Model 26, stopping the wheel when the character was
in front of the paper so the hammer could hit it.  And they didn't have
the kinds of plastics that eventual daisy wheel printers used.  There
was also the NEC Spinwriter, with the daisy wheel formed into a cup shape.

> The Extel was mentioned
> above.

Some of the Extel printers required special paper.  3M developed a paper
in which the ink was encapsulated in little white "eggshells".  Hitting
the eggshells broke them and let the ink appear.  Then they apparently 
also made some with conventional ribbon, since the special paper was quite
a bit more expensive than the regular kind.  I have an Extel printer in
the collection, but unfortunately it is the special paper kind.

> included the DeskFax that Western Union gave to customers to send their
> telegrams to the local office. It had a classic spinning drum for
> scanning.

Western Union developed a special paper they called Teledeltos which
had a white coating over a black conductive core.  It was possible with
fairly high voltage to spark through the white coating to make black
marks.  There was some concern over whether toxic fumes were released
in the process.

> I think these were made by Alden (
> http://www.alden.com/about - Looks like they were acquired by Morcom ).
> These printed by passing current through soggy paper turning it from white
> to brown. Horizontal scanning was provided by a drum with a helix on it.
> The drum and helix were behind the paper and a "blade" was in front of the
> paper. When the helix was in the right position, a voltage would be put on
> the helix causing a current through the soggy paper turning that spot
> brown.

   There were two companies in the wet paper business, Alden and Hogan.
Hogan used a paper called "catechol" that produced a black mark.  Alden
said the stuff was toxic and also claimed their sepia print was more 
readable.

>
> This FAA flight service station also had a bunch of Teletypes. The staff
> would do weather observations, punch a paper tape, then load it into a
> tape reader. The reader would be polled by some FAA center and the tape
> read.
>
They also handled flight plan information by Teletype.  Back in those days
of vacuum tube electronics the air traffic control centers had limited
radio communication with airplanes, and limited radar contact.  So 
airplanes flying under instrument rules had to report their positions
by radio to the manned flight service stations, which then informed the
traffic control centers.  Nowadays the traffic control centers have remote
radio stations all over the countryside and have almost complete radar
coverage of the air routes.  Most of the flight service stations are gone,
with a few remaining to provide services to airplanes and using remote
radio facilities.