[GreenKeys] news wire photos

[Lee Mushel]

Ya know, I'm beginning to suspect that I'm the only reader of this reflector 
who has actually hands on sent and received one of these old fax images. 
If you push me much harder I might even have to take a few photos of my 
efforts of  40 years ago!

Lee   K9WRU
----- Original Message ----- 
From: "Jones, Douglas W" <douglas-w-jones at uiowa.edu>
To: "Rokumon Cat" <rokumoncat at yahoo.com>
Cc: <GreenKeys at mailman.qth.net>
Sent: Thursday, June 16, 2011 2:24 PM
Subject: Re: [GreenKeys] news wire photos


>
> On Jun 16, 2011, at 1:41 PM, Rokumon Cat wrote:
>
>> Hi,
>>
>> I was wondering, how did "they" send photos over the news wires in the 
>> forties and fifties?
>
> With a telefax machine, of course.
>
> Fax machines are old technology.  Alexander Bain and Giovanni Caselli 
> developed
> this technology in the mid 19th century.  That's before the telephone. 
> The
> first commercial fax service was introduced using Caselli's Pantelegraph. 
> The
> first "pantelegram" was sent from Lyons to Paris in 1862.
>
> The Pantelegraph used synchronized pendulums at the transmitter and 
> receiver.
> So, you have sync pulses on the line at the end of every scan line to keep 
> them
> in sync.  The scanner required that the original be done in conductive 
> ink,
> but it could scan drawings or handwritten text equally well.  The sync 
> pulses
> also advanced the paper.  At the receiving end, an electromagnet raised 
> and
> lowered the pen that recorded the result.
>
> The communications line used was a regular telegraph line, so there was no
> transmission of gray scale images.  Just black and white.
>
> Now, move forward a century, to the Teletype-brand wire-service telefax 
> machine
> that I recall seeing in the Museum of Science and Industry in Chicago back 
> in
> the early 1960s.  The paper paper transport was essentially the same as 
> used on
> a teletype, except that the line-feed was one scan line instead of one 
> text line.
> It used a regular cloth ribbon too, but instead of a print hammer, it had 
> a
> spiral bar (one half twist in the width of the page) so that there was 
> only one
> point on the bar that was over the rather sharp metal edge of the platten 
> at any
> instant.  The bar spun at a constant rate (synched to the synch pulses in 
> the
> signal) and whenever it was supposed to record a black spot, the spiral 
> bar,
> ribbon, paper and platten were pressed together.  We're talking about 96 
> pixels
> per inch resolution, so at baud rates under 300 baud typical of that era, 
> we're
> talking about a fairly slow fax machine.
>
> The scanners used to transmit the image typically required that the 
> original
> be mounted on a rotating drum.  This would spin as a lead screw advanced 
> the
> photosensor across the face of the drum, with a cam on the drum producing 
> the
> sync pulses.  The fax standards used in that era are still around.  We 
> call them
> the Group 1 (6 minute per page) and Group 2 (3 minute per page) standards.
>
> Doug Jones
> jones at cs.uiowa.edu
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