Ancient Teletype Revived in Labor of Retrocomputing Love

Readers with not too many years under their belts may recall a time when the classic background sound effect for radio and television news programs included a staccato mechanical beat, presumably made by the bank of teletype machines somewhere in the studio, clattering out breaking stories onto rolls of yellow paper. It was certainly true that teletypes were an important part of the many communications networks that were strung together over the 20th century, but these noisy, greasy beasts had their day and are now largely museum pieces.

Which is exactly where the ancient Model 19 Teletype machine that [CuriousMarc] and company are restoring is destined. Their ongoing video series, six parts long as of this writing, documents in painstaking detail how this unit worked and how they are bringing it back to its 1930s glory. Teletypes were made to work over telephone lines with very limited bandwidth, and the hacks that went into transmitting text messages with a simple 5-bit encoding scheme are fascinating. The series covers the physical restoration of the machine, obviously well-loved during its long service with the US Navy. Of particular interest is the massive power supply with its Thyratron tubes and their mysterious blue glow.

The whole series is worth a watch if you’re even slightly interested in retrocomputing. We’re particularly taken with the mechanical aspects of these machines, though, which have a lot in common with mechanical calculators. [Al Williams] recently covered the non-replacement of the power supply caps for this unit, which is an interesting detour to this restoration.

17 thoughts on “Ancient Teletype Revived in Labor of Retrocomputing Love

  1. I remember different versions of these machines in radio stations I worked at in the 1970’s. Those looked similar but didn’t have keyboards. Noisy and greasy indeed. The ones I saw had a type of acoustic-insulating shroud that cut the noise but made them run hot (the big motor) with an oily smell wafting nearby. Thanks for the video!

  2. “Readers with not too many years under their belts may recall a time when the classic background sound effect for radio and television news programs included a staccato mechanical beat, presumably made by the bank of teletype machines somewhere in the studio, clattering out breaking stories onto rolls of yellow paper.”

    Lovely way to start a morning with a “get off my lawn” moment. Now I feel old too. Next up the sound of a Morse-key.

  3. I had a Model 15 (basically the same as that ’19) for many years. Noisy, smelly, hot, glorious device. It last did service as a printer for my VIC-20. Slow as heck, around 8 characters per second. Made me utter the phrase “Waiting for Baudot.”

    But still not as slow as the 1 character-per-second TWX (Telex) machine we had at work for transatlantic comms, when the 3-minutes-per-page analog fax was too expensive (a half day’s pay per page!) or unreliable.

    I threw that Model 15 off a cliff when I moved houses. It’s in the geological strata now. I sometimes think it would be cool to have kept it, but then sanity returns.

    1. In my teenage years I had a big old teletype as a printer too. Every time it did a carriage return after a long line it would creep along the table a little, until one day the inevitable happened…it too fell off a cliff, well the end of the table, but the outcome was similar.

  4. So does modern linux still support 5-bit terminals? You can set 5-bit mode in termios, but do the characters get translated properly? This used to work, I’ve seen ancient Unix boxes with 5-bit teletype consoles.

    1. termios will not translate the character codes. Also, keep in mind that Linux is a “Unix-like” kernel, and the additional tools required to make it an operating system, like the GNU tools, are very specifically “GNU’s Not Unix”. So any feature that was already considered obsolete before GNU/Linux was developed, probably isn’t there.

      Regarding implementing this if it’s not there (and it doesn’t look like it’s there), there’s a difference between using an old Teletype to accept input and generate output over a serial port, versus using it as a standard terminal device, i.e., being able to use it to enter shell commands and even use it as the system console. This guy,, uses it in the former sense, using a current loop to RS-232 interface (very simple hardware) to connect to a serial port, and a Perl script to do the Baudot to ASCII conversion. I did something like this decades ago, to use a Selectric typewriter as a letter-quality printer for my TRS-80 Color Computer, and it wasn’t difficult. The other part – getting the system to treat it as an ordinary ASCII terminal, might be possible using ncurses and/or terminfo, but the man pages for those are all about building interfaces to ASCII-based terminals in order to take advantage of their cursor-control codes, with no mention of actual character code translation.

      Even if it would turn out to be a rabbit-hole using GNU/Linux’s built-in tools, there’s still another option: it would be a pretty simple application to develop for an AVR or PIC microcontroller, to accept current loop input at an archaic baud rate (45.5???), convert the character set, and transfer that to its standard serial port at a more modern baud rate, and with 7-bit encoding. One usability challenge would be that Baudot code has no provision for lower-case letters, which are kind of important in Linux, so some convention would have to be developed for generating non-Baudot characters using Baudot character sequences.

  5. Worked for Pacific Bell as a TTY repairman and at a 82B1 TTY switching center/ Loved working the on mechanical equipment. etc.. One not so happy memory was a Model 28 RO at a stock brokers office They used mimeograph paper in it and everything was always coated the that @#$##@ blue ink.

  6. The model 28 was a wonderful piece of engineering. It had a type-box that it moved around in front of a fixed striker. On both of these machines, the timing and thus the baud rate is determined by the motor speed and gearing. So, it was “hardwired” in the most basic mechanical sense. The data signal was a current loop serial connection, either 20 or 60 ma, so it ran something like 100 volts or so and could be driven by a vacuum tube.

    It is a bit humorous listening to the running commentary by people who are just now discovering the functions of each piece

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.