The April 1926 issue of “Science and Invention” had a fascinating graphic. It explained, for the curious, how a photo of a rescue at sea could be in the New York papers almost immediately. It was the modern miracle of the wire photo. But how did the picture get from Plymouth, England, to New York so quickly? Today, that’s no big deal, but set your wayback machine to a century ago.

Of course, the answer is analog fax. But think about it. How would you create an analog fax machine in 1926? The graphic is quite telling. (Click on it to enlarge, you won’t be disappointed.)

If you are like us, when you first saw it you thought: “Oh, sure, paper tape.” But a little more reflection makes you realize that solves nothing. How do you actually scan the photo onto the paper tape, and how can you reconstitute it on the other side? The paper tape is clearly digital, right? How do you do an analog-to-digital converter in 1926?

It Really is a Wire PHOTO

The graphic is amazingly technical in its description. Getting the negative from Plymouth to London is a short plane hop. From there, a photographer creates five prints on specially-coated zinc plates. Where the emulsion stays, the plate won’t conduct electricity. Where the developer removes it, electricity will flow.

Why five? Well, each print is successively darker. All five get mounted to a drum with five brushes making contact with the plate. Guess how many holes are in the paper tape? If you guessed five, gold star for you.

As you can see in the graphic, each brush drives a punch solenoid. It literally converts the brightness of the image into a digital code because the photographer made five prints, each one darker than the last. So something totally covered on all five plates gets no holes. Something totally uncovered gets five holes. Everything else gets something in between. This isn’t a five-bit converter. You can only get 00000, 00001, 00011, 00111, 011111, and 11111 out of the machine, for six levels of brightness.

Decoding

The decoding is also clever. A light passes through the five holes, and optics collimates the light into a single beam. That’s it. If there are no holes in the tape, the beam is dark. The more holes, the brighter it gets. The light hits a film, and then it is back to a darkroom on the other side of the ocean.

The rest of the process is nothing more than the usual way a picture gets printed in a newspaper.

If you want to see the graphic in context, you can grab a copy of the whole magazine (another Hugo Gernsback rag)  at the excellent World Radio History site. You’ll also see that you could buy a rebuilt typewriter for $3 and that the magazine was interested if the spirits of the dead can find each other in the afterlife. Note this was the April issue. Be sure to check out the soldering iron described on page 1114. You’ll also see on that page that Big Mouth Bill Bass isn’t the recent fad you thought it was.

We are always fascinated by what smart people would develop if they had no better options. It is easy to think that the old days were full of stone knives and bear skins, but human ingenuity is seemingly boundless.  If you want to see really old fax technology, it goes back much further than you would think.