[GreenKeys] news wire photos

[Jim Haynes]

On Fri, 17 Jun 2011, Nick England wrote:

> in magazines, etc. For actual gray-scale photos, the receiving paper
> was regular light-sensitive photographic paper and a variable
> intensity lamp was focused to create the spot on the paper. Lamp
> intensity was determined by the incoming AFSK frequency (1500-2300
> cps)
> After reception, the paper was developed using normal photo chemicals
> in a darkroom.
>
And, in that day, all the newspapers had darkrooms for developing their
own photography, so developing the fax images was no extra burden.

The "spark" type paper, actually Western Union Teledeltos, was not
developed until the late 1930s.

Then into the 1960s there was a technology using electrolytic recording
on wet paper.  The images were gray (Hogan) or sepia (Alden) and of
rather poor contrast either way.

Related to all this is the transmission issue.  If a company like AP
leased private lines from the telephone companies to their subscribers
they could send tone-modulated signals or whatever they wished, within
the bandwidth allowed by the circuit.  Typically the receivers had to
generate their own power for running the drums, because commercial power
frequencies were not synchronized.  So a signal had to be sent over
the wire for synchronizing the motor drive.  This could be complicated
if the telephone circuit passed through carrier channels, because
carrier channels often introduce a frequency offset.  Even with
synchronized commercial power grids there can be phase shifts in the
system.  There is an awful lot of material in Western Union Technical
Review about the difficulties of transmitting fax over a distance.

Then if you need to avoid private lines and use the switched telephone
network...well the "no foreign attachments" rule sets up hurdles for you.
I've seen pictures in an encyclopedia of acoustic coupling a fax system
to a telephone.  I guess the telephone companies grudgingly tolerated
this mode of operation, since, after all, there was money to be made
from a long distance phone call transmitting a picture.  Then in the
early 1960s when AT&T started supporting non-voice services by leasing
modems (data sets) for use on the switched network, there was one
specifically for fax.

Some company attempted to set up a nationwide fax service based in
agencies and transmission over the switched network.  For a fee they
would transmit your image from one agency to another, and the recipient
could pick up his copy at the receiving agency.  This was in the days
of wet paper recording; so I don't think the idea ever went anywhere.