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This is slightly tangential, but it's Atlantic-cable-related, and I just learned about it. Let me set the stage. By the 1920s, analog fax technology was established and there were a variety of experimental and early commercial systems in use. One of the first uses of modems was to transmit faxes over the long-distance telephone network, turning a voltage into a pitch, and vice versa. The electronic marvel of the 1930s in the newsroom, aside from the teletypes, was that you could take a photo in San Francisco and have it published just hours later in New York.
But how do you get a picture across the Atlantic Ocean? Those analog fax systems suffer from noise and in the experimental systems of the 1910s and 1920s long-distance was impractical. Shortwave to get over the Ocean was right out. There were no transoceanic telephone links. But there were submarine telegraph cables. Morse code or Baudot telex. Not very fast with no amplifiers along the lines yet. But you could send a telex across the Atlantic ocean.
Enter the Bartlane transmission system. First, five photographs were developed from the original negative, at different exposure levels, using a conductive developer. So each point of the image is more or less conductive depending on its exposure. Each of these photos is scanned, as if it had pixels, and a 1-bit intensity value collected for for all five photographs, creating a five-level greyscale bitmap image on tape basically. (Five bits worked with existing Baudot code equipment.)
This enormous tape was then sent over the wire. On the receiving end a printer, with intensity controlled by the level indicated, would then selectively expose a spot on a photographic plate to light, as it stepped through the tape. Six hours to send a small image. But digital was the only way to send a photograph from London to New York overnight from its early trials in the 1920s until the 1950s.
By chiph 2021-09-251:49 > Six hours to send a small image.
Imagine the price of exclusive use of a transatlantic telex line for that length of time! Teleprinters back then commonly ran at 50 baud, so a 400x300 dot photo would take a little more than 40 minutes (120000 dots / 50 baud / 60 seconds)
The linked article mentions that the punched tape could be cut into several pieces then transmitted in parallel over several telex lines at once. At the receiving end the punched tapes would be spliced back together in correct order, and then used to create the photographic negative.
That's an interesting piece of historic technology. Thanks.
By andrepd 2021-09-251:39 Wow, that's insane.
By axiosgunnar 2021-09-2420:50 Interesting
By neilv 2021-09-2415:56 Cool. We take it for granted, but the intercontinental data (and voice) connectivity cables are an impressive achievement for humanity -- technical, and for global community. And globe.gl has me "seeing" for the first time a particular cable for which I have a much smaller personal story.
One of those submarine cables being severed accounts for one of only two software/hardware downtimes for a B2B startup's launch MVP, which had been deployed in critical production overseas.
Our station appliances at the facility needed to talk with servers (at the network-closest AWS AZ) multiple times a minute, for cryptographic security reasons. The appliances had a boot-time check for network connectivity (which saw extreme latency and packet loss as network unavailable). For reasons, the facility powered off all equipment at night.
One day, the facility said the appliances wouldn't "turn on", I quickly found they were having network problems, but facility insisted their LAN and Internet connectivity was fine. I was able to carefully SSH in (with terminal responsiveness like a bad dialup to an overloaded timesharing system), and relaxed the timeout on the check that was in a retry loop, and the stations came to life (albeit network requests during operations much slower than normal). The facility manager advised later that day that it turns out a submarine cable had been severed.
It's kind of hard to distinguish between land and water when they are both black. Improving the contrast or adding a border would help.
By contravariant 2021-09-2413:553 reply Indeed, especially for those few spots seemingly in the middle of the ocean where the cables converge it would be interesting to know what land masses (if any) are nearby. Right now this is very difficult to see.
By skeeter2020 2021-09-2416:20 I actually think there's a real unique and distinctive visualization caused by this decision. We're typically very geo-politically focused when we look to evaluate this sort information, but think about it without differentiating between land and ocean, without countries or borders. Think of nodes and edges in a graph, with the size/volume of edges weighing priority. Totally different way to view "earth".
By rkuykendall-com 2021-09-2719:30 Switching between this and Google Maps the answers appear to be, predictably in hindsight, Hawaii / Guam / American Samoa.
By intpete 2021-09-2417:25 It appears to be Guam.
