[GreenKeys] Telephoto machines?

[David I. Emery]

On Sat, Jun 27, 2015 at 07:25:20PM -0500, Jim Haynes wrote:
> 
> The WW-II era AN/TXC-1 was a photo-quality machine used by the military.
> I imagine it was derived from a civilian machine, but I don't see anything
> in the tech manual that identifies the supplier.
> 
> There was, I believe, a company called Times Facsimile.  Nick England's
> web site mentions some fax equipment used by the Navy and made by Times
> Facsimile.  I wonder if that was a subsidiary of the N.Y. Times.  There
> was also a Times Wire & Cable Co. that made coaxial cables among other
> things.

	I played around a bit in the early to mid 60s when in HS with
some old Times photofax gear of the sort that was once used for
wirephoto distribution.   Used a fancy neon lamp (called a crater lamp
for the bowl shape of the electrodes) focused with a microscope
objective lens on a metal drum around which one wrapped sheets of
photographic large format film (or photo paper).   The drum was turned
by a special phonic wheel motor driven by a big AC power amplifier from
a tuning fork oscillator (or in my case a VCO locked to a reference) and
a lead screw mechanism moved the drum along its axis past the lamp and
lens.

	There were various standards in use for these things at the
time, early ones were 60 RPM drum speed, later they went to 120 RPM
IIRC.

	The lead screw pitch/rotation rate also varied as different fax
systems used different scanning density (something called the "index of
cooperation".

	The crater lamp was designed to have a suitable known curve of
light output versus drive voltage and current... and with the correct
electronics driving it could accurately reproduce a gray scale over a
couple of decades of optical density at least.

	The rotation rate of the synchronous phonic wheel motor was
controlled by the AC drive frequency which was derived from a tuning
fork or crystal standard as the line frequency is actually remarkably
unstable and off much of the day... and the phasing of the drum rotation
was controlled by a mechanical slip clutch released by a magnet driven
from the incoming signal before a photo transmission which carried a
once per rev sync pulse designed for this purpose.   

	The actual line signal was a 1500 or 1800 Hz AM modulated
carrier, with start stop and control and phasing info on other lower
frequency tones.

	These early machines were pretty manual, one loaded the film in
a dark room and waited until the start tones and phasing occurred and
started up the drum - then engaged a clutch to start the lead screw when
actual image info was transmitted.   An operator had to be present to
change the film (and develop it) and start up a new reception.

	There was sometimes actual speech audio on the wireline circuit
announcing specific image transmissions I understand... the machines I
had had a monitoring speaker for this.

	Later generation machines used rolls of dry photo paper fed past
a mirror scanning mechanism... and could print multiple photos on the
paper as it went past in one long roll.   I believe there were also film
machines of that era that did this on rolls of film that could be later
developed and used to create halftones.

	I remember seeing the roll of paper machines in newspapers and
TV newsrooms in the 60s/70s... I believe the paper prints were mostly
for editorial use, and they actually used film for creating the printing
plates/halftones so both were sometimes captured.

	And I know in addition to the actual dry photo process there
were some machines used for this that used wet electrolytic processes
similar to the ubiquitous Alden reddish brown images used universally in
weather forecast offices and aviation FSS and other pilot briefing
facilities for weather maps.   I think one maker of these was Fairchild,
but memory fades with age...

	AM transmission (both originally DSB, and later I believe a VSB
system) on voice grade circuits was standard for newspapers and TV
stations - but there was a good bit of HF radio wirephoto transmission
to overseas subscribers that used FM instead.   Much of that was 60 or
sometimes 90 RPM... rather than 120 RPM.

> 
> Ah, yes, I see a web page www.hffax.de/history/html/facsimile_makers.html
> Perhaps answers all the questions.
 
> There were fax companies Alden and Hogan Faximile, but I don't know if
> they made photo-quality equipment.

	Alden more or less owned (at least in the USA) the market for
machines used to distribute weather maps and later made a lot of
machines used for displaying APT and WEFAX weather  satellite photos as
well.    These worked with a spring loaded helix wire wrapped around a
rotating drum that formed a contact point with a thin ribbon of
stainless steel on the other side of the paper (the paper was pressed
between the helix wire and the steel ribbon blade by springs and pulled
past them by motorized rollers). 

	The paper was wet, and soaked with an electrolyte and current
was driven through it between the blade and the helix, which caused a
chemical reaction with iron from the blade that produced the reddish
marks.   Later chemistry made bluish markings toward the end of the
Alden era.

	Alden machines were sometimes used for other things, but the
great majority of them were used at virtually every airport and weather
forecast office and flight service station in the US and most major TV
stations and many universities.   I don't believe they tried very hard
for high quality photo grade image reproduction... though there were
other electrolytic machines and chemistries that were pretty good.

	Signaling for the weather maps was originally similar to the
early wirephotos but eventually was converted to a compressed digital
format called Difax sent over early digital voice grade modems and later
over VSAT satellite circuits - until the whole infrastructure was
replaced with computer imaging and electronic weather maps in the 1990 -
now all of this stuff is high speed IP over a geo satellite broadcast
in modern digital image formats (and of course over the Internet as
well).

	I have never seen a Hogan machine... or know much of anything
about their markets.

	I don't know at what point press wirephotos were converted to
other forms of transmission (56 kbs) but I do remember reading that a
color higher quality faster technology was introduced sometimes in the
80s or 90s.  I do, however, know that at least some of the modified AM
analog voice grade wireline stuff was around into the mid 80s more or
less... with VSB modulation and more sophisticated signal structure
IIRC... and maybe 240 RPM.

	Recently almost all of this wire service stuff is now
distributed by Internet... in the usual Internet photo formats along
with the actual wire copy that used to be printed on TTYs... and of
course now a lot of video clips.    The various photo encoding and file
formats are more or less the same as used for other images on the net.

	Satellite broadcast transmission of digitized news video clips
was common until very recently but most of this has also migrated to
on-demand cloud servers rather than geo satellite broadcasts.	

>  Then Western Union spent tons of
> money on fax development, but I don't know if they got into photo quality.
> They were more interested in fax as a way of handling messages.

	Aside from news wirephotos and weather photos the other major
customers for photo quality fax back then were the military and the 
intelligence community... there wasn't a whole lot of use of electronic
image transmission for other civilian purposes - partly because images
took a lot of bandwidth which was very costly back then... and compression
technology was in its infancy and expensive and complex for the era.

	Of course the 70s and early 80s saw a huge explosion in the use
of digital fax for messaging... over regular POTS lines.



-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."