How were photos transmitted by wire in 1937? | Hacker News Reader

How were photos transmitted by wire in 1937?

thekidshouldseethis.com

47 pointscaseysoftware10 comments

I saw this movie and was interested at the tech that climb the telephone pool to hookup the transmitter.

Was this a common thing back in the day? Did random poles have equipment that non-telephone company people could hook into for remote use like this? I can think of many different use cases for this in the days before widespread mobile telephones.

I'm pretty familiar with telephone history and technology but can't seem to find references to these or what they where called. Anyone have any pointers?

This was the 30s, with phone lines decades? older, so would they even be waterproof? I guess they could use asbestos and wax or something, but this was before wide scale platic.

Rubber coated maybe?

I guess my point is, that you could tap into the line without breaking it. And rubber coating on a wire after a decade in the sun, would have lots of cracks?

Again, these wires would be a decade or more old. 1900 tech? Would they even be coated?

Few people even had phones. Party lines for a whole rural town were common. And you could separate lines with spacers.

Anyhow. I think they just tapped into the wire.

Maybe they just slapped some liquid rubber after tapping?

It looked like there was a box on the pole they were hooking into made for this purpose.

Amateur radio operators are still using a related system: https://en.wikipedia.org/wiki/Hellschreiber

Newspapers were still using the same system up until the late 1980's. The AP (Associated Press) Leafax transmitter debuted in 1988, allowing a photographer to scan the processed film, instead of making a print. The photographer then could send that image to an attached receiver or transmit it over a conventional telephone line. That tech made its way to daily newspapers in the early 1990's.

Damn it was explained so well a child could understand it. Interesting how the photoelectric effect came into play here.

Also from what (little) I understand we are kind of doing the same thing, but with pixels now.

Yep, pretty much.

My kids know how to play Battleship so I had explained it using that:

- Instead of hunting ships, if you give the coordinates, you could make pictures.

- If you give coordinates+colors to place there, you could make better pictures.

- If you make the squares smaller, you can make even better pictures.

With the process in the video, you "skip" the coordinates because it's sequential and the only signal you're sending is darkness/lightness of the original.

An explanation of how the lines were synchronized between the reading and writing drums seems to be glossed over. Anyone know how they did it?

I can only guess, but, to borrow TV nomenclature, synchronizing was probably based on the horizontal blanking interval. That is, the period between lines that is most black because it's scanning the dark drum in between ends of the paper. This looks be slow enough that the operator could very well synchronize the receiver manually.

Otherwise, relying on mains frequency to control other parameters, same as TV.

The fundamental principles of this tech very much resemble TV, just with a single frame and very slowly.

Is that the Chevrolet logo at the end?

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