Messages From Hell: Human Signal Processing

Despite the title, there’s no religious content in this post. The Hell in question is the German inventor [Rudolph Hell]. Although he had an impressive career, what most people remember him for is the Hellschreiber–a device I often mention when I’m trying to illustrate engineering elegance. What’s a Hellschreiber? And why is it elegant?

The first question is easy to answer: the Hellschreiber is almost like a teletype machine. It sends printed messages over the radio, but it works differently than conventional teletype. That’s where the elegance comes into play. To understand how, though, you need a little background.

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Retrotechtacular: A Mechanical UART

We’ve heard it said that no one invented the old mechanical Teletype. One fell from the sky near Skokie, Illinois and people just duplicated them. It is true these old machines were similar to a modern terminal. They sent and received serial data using a printer instead of a screen. But inside, they were mechanical Rube Goldbergs, not full of the electronic circuits you’d think of today.

Teletype was the best-known name, but there were other mechanical monster terminals out there. [Carsten] recently took some pictures of his 99 pound Olivetti mechanical terminal. According to him, there’s only one electronic component within: a bistable solenoid that reads the data. Everything else is mechanical and driven with a motor that keeps everything at the right baud rate (110 baud).

Like the Teletype, it is a miracle these things were able to work as well as they did. Lacking a microcontroller, the terminals could respond to an identity request by spinning a little wheel that had teeth removed to indicate which letters to send (TeleType used a similar scheme). Things that are simple using today’s electronics (like preventing two keys pressed at once from being a problem) turned out to be massive design challenges for these old metal monsters.

Turns out that when [Carsten] last fired the terminal up, a capacitor finally gave up its magic smoke. He plans to fix it, though, and as long as it isn’t a mechanical problem, we bet he will.

We’ve talked about Teletypes a few times in the past, including using them for text messaging and even Twitter.

Pre-Web Hardware Connects To The Web

We’re not quite to the 25th anniversary of the world wide web, but that doesn’t mean the greatest innovation in information distribution since [Gutenberg]’s press can’t be celebrated a bit early, does it? [Suhayl] is throwing some of his hardware into the ring, and loading up the first web page with a modem from the mid 1960s and a teletype from the mid 70s. No, no sane person would have ever done this 25 years ago, but it’s neat to watch in any event.

The hardware [Suhayl] is using includes a Livermore Data Systems modem. It’s a finely crafted wooden box with an acoustic coupler on top, and a DB-25 connector on a side that connects to a terminal or computer via RS-232. If that Livermore Data Systems acoustic coupler modem looks familiar, you might be right. This modem was demoed back in 2009 by [phreakmonkey]. It’s an impressive little box that can connect to a remote system at up to 300 baud.

The I/O is handled by an ASR-33 teletype. This was the standard way to connect to computers and mainframes before we were all blessed with video terminals and TV typewriters. The whole setup connects to a Unix system with a much more familiar Hayes modem, runs a text-only browser, and retrieves the first web page as it was served up at CERN some 25 years ago.

Having fun with dumb terminals


For a long time now, [Morgan] has been wanting an old serial terminal. In a stroke of luck, one of his pals at the Quelab hackerspace scored an awesome ADM-3A terminal from a collector. It’s a historically significant piece of computing and UNIX history, so obviously [Morgan] needed to get it working.

The ADM-3A terminal pre-dates the famous DEC VT-100 terminal, but since [Morgan]’s new acquisition speaks RS-232, he had a good shot at getting it to work with one of his more modern boxes. He’s using a Windows laptop loaded up with FreeBSD in a VM to talk to the terminal. Surprisingly, the only additional hardware required was a USB to serial cable and a DE9-DB25 serial adapter.

It may not be as cool (or as loud) as Quelab’s Teletype ASR-35 they have set up for Zork sessions, but it’s great to see ancient hardware have some
use. Right now, [Morgan] is editing files with vi and of course playing Zork. Seems like there’s plenty of life left in this old dumb terminal. After looking for an old VT-100 for a while now, I’ve got to say I’m pretty jealous.

Only losers text message on cellphones – this guy carries his own teletype for that

Yes, that’s an SMS text messaging device. [Mdziewie] decided that texting on a regular cellphone was too boring and decided to build himself an old-school SMS gateway. Here’s a translated link but the formatting of the forum post gets screwed up with the machine translation.

The device he’s using is an ASR-33 Teletype machine, which was introduced to the market in 1963. It is connected to a GSM modem via an ARM microcontroller, the STM32F103. This chip, along with a few electronic components, let [Mdziewie] design an interface that doesn’t require alteration to the ancient hardware. The forum post linked above includes video of this sending and receiving texts. It’s awesomely loud as it hammers away at the paper, and seems to work as expected.

If you hunger for one of your own but don’t have half-century old equipment there’s still hope. Find yourself a typewriter and turn it into a teletype machine.

Teletype Twitter frontend

The folks from NYC Resistor got their hands on a teletype machine and hacked it to monitor Twitter. This eighty-year-old beast bangs out messages that it receives at 45.45 baud. This isn’t a project that turns something into a teletype, but rather finds a different way to feed the machine data. In this case, a python script parses Twitter and sends the data it finds to an Arduino board. The Arduino in turn formats the message into the serial format necessary to communicate with the device. To the left you can see a trend plotter, learn more about both in the video after the break.

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Teletype machine from an electric typewriter

This project, by an unknown hacker, patches into an electric typewriter and uses it as a Teletype. An AVR ATmega168 microcontroller patches into the key matrix of the typewriter which allows it to artificially type. Now, data can be sent over a serial connection to the AVR for output on the typewriter.

We’re not quite sure what this is going to be used for.  We’ve seen hacks like this for Twitter reading in the past but he makes no mention of that type of use. Personally, we’d like to have this just to “print” out the occasional letter. Typewriters are so rarely used these days it would be a bit peculiar to get a letter that has the dimpled impressions associated with slamming a die into a piece of paper.