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 establi

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. http://www.hffax.de/history/html/bartlane.html http://www.hffax.de/history/html/bartlane.html