[GreenKeys] news wire photos

[Sheldon Daitch]

On 6/17/2011 9:31 PM, David I. Emery wrote:
>
> 	Transmission over HF radio was FM (FSK), transmission over
> leased wire lines was usually DSB AM with a carrier tone of 2400 Hz
> being common or sometimes 1800 Hz.   More tone, brighter light usually I
> think.
>    

I don't remember the frequencies used by the AP or UPI, but I do know 
they were different.
I was on an AP wirephoto service call at a newspaper in eastern North 
Carolina and cleared the
problem with the machine, and I was waiting for it to print out a photo 
or two before I left and
lo, it still didn't work.  I listened a bit to the talk up on the wire 
circuit and realized I did not
recognize the terms used for sending and receiving points.  A call to 
AT&T revealed the
circuit was being fed by the UPI wirephoto network.  After that was  
straightened out, the
wirephoto machine worked find.
> 	Early drum and lamp fax machines could use either sheet film or
> photographic paper depending on the need...  I believe film was quite
> common for newspaper use...
>
> 	Some late era photo fax and wirephoto machines used dry silver
> paper developed by heat and fed from a roll rather than wrapped around a
> drum.   Spinning mirrors provided a scan.    And for lower quality
> images there were always the helix-on-drum moist paper electrolytic
> machines widely used for weather maps
>    

The AP office in Raleigh had one machine of the helix-on-drum  wet paper 
type in the
front news room.  I cannot remember the manufacturer's name, but I do 
remember it was
made in Japan.  At this point, 1978, the AP had pretty much converted 
the entire state, maybe
nationally, from the old style machines to the newer LaserPhoto machines 
made by Harris.

These units used the dry silver heat developing process and a well set 
up receiver printed
out wirephotos which were of exceptional quality.  Paper was indeed a 
roll type product and
there was a cutting bar which cut the paper after each photo.


> 	Early machines were manually operated with a speaker to monitor
> the line inside the darkroom allowing the operator to load the film or
> paper and start the drum spinning and activate the magnet driven clutch
> mechanism that would allow the receiving machine to acquire phase
> synchronism with the sending machine as the sending operator set up to
> start transmission.
>
> 	Later machines (especially the roll paper kind) used audio
> signaling tones to control start and stop of reception and initiate
> phasing.
>
>    

      I never worked with the manual machines.  The wet paper and the 
dry silver machines from
the 1970s era were all automatic and roll fed.
> 	
> 	DSB AM audio tone wirephoto networks were around into the early
> 80s at least - used with automated printers, I do not know if there ever
> was a digital version developed for wirephotos as there certainly was
> for documents and weather maps.    More recently wirephotos are sent
> over TCP/IP on Internet or private connections as .jpegs or similar just
> as all kinds of other images are.
>
>
>    
One of the issues with the audio tone level networks is that any level 
shifts in the leased telco network
resulted in a shift in the gray scale of the photo.  Bear in mind, I 
haven't thought about this in over 30 years,
There was a setup sequence transmitted by each sending machine, which 
synchronized all the receiving
machines and a gray scale step test, about 15 steps between black and 
white, to calibrate the machines
for, well, gray scale.

I had asked why the AP stayed with tone level instead of going FSK and 
was told they wanted to stay
with the tone level, for old and new machine compatibility and that 
digital was going to be the next
step.  I would now think the wire photo process is much different than 
it was then.

73
Sheldon