Marty! You’ve Gotta Come Back With Me!

Telecom Time Machine

Like any good plan, you should always start with the intention to build a time machine. That way if your future self succeeds, your current self doesn’t have to worry about actually doing it!

Well, unfortunately it hasn’t quite worked out for hosts of [Toymaker], but they have managed to make a pretty authentic Telecom Time Machine instead!

What they’ve created is something called a “dumb terminal”. Back in the days of yore before personal computers existed, if you wanted to get “online” you would have to do so at a dumb terminal. It’s essentially a monochrome monitor, a keyboard, and a serial port. You would have to actually connect to the mainframe to do anything — but back then, you couldn’t just hook up a modem — oh no, you had to use an acoustic coupler to connect. You had to play sounds through your telephone in order to communicate with the mainframe. How’s that for a bit of history with your morning coffee!?

Using a Raspberry Pi 2, they built a dumb terminal emulator — but not wanting to take the easy way out, they actually used a real acoustic coupler to communicate with a modem! It wasn’t easy.

This project has been a few years in the making — with most of the time used to collect all the components they would need for the project; including:

  • Antique Telephone (G type handset)
  • 300 Baud Acoustic Coupler Modem
  • DTMF Tone Generator
  • Private Branch Exchange
  • Green Phosphor Cathode Ray Tube Monitor
  • Model M (buckling-spring, clicky) Keyboard
  • AT to PS2 Keyboard Adapter
  • PS2 to USB Keyboard Converter
  • External USB Fax Modem
  • Raspberry Pi Dial Up Server
  • Raspberry Pi Dumb Terminal
  • Seamstress Computer Desk

We’re impressed. Check out the video — and you will be too. Of course we’re always flattered when people fix up old hardware and use it to load up the Hackaday Retro Edition. Nice work tymks!

And the terminal in action of course!

19 thoughts on “Marty! You’ve Gotta Come Back With Me!

    1. The terminal side Raspberry Pi isn’t required. For our test set up, we were actually using a Propeller MCU to handle the serial with the acoustic coupler, handle the key strokes, and generate an ntsc signal for the monitor. This worked great for almost everything, but the prop based terminal emulator still needs a few of the ‘fancy’ features implemented. You can find video of us testing sans-pi on the channel.

    1. It’s Acer’s 1990 version / copy of the Model M, and yes it is buckling spring. Related: Kev is bringing over an IBM terminal keyboard tonight. We’re going to see if that fits and if it will play well with the pi / picocom.

  1. The terminal update was WAYY too fast to be 300 baud. For those of us who remember what dialup was like, running a terminal at 2400 baud was still slow, his screencap is unauthentic!

    1. The screen cap is from our Telehack LP series, not part of the demo. I don’t know why it got tacked on to the end of the article, but any extra exposure to such a cool project is good.

      The stuff from the first video is through the acoustic modem @ 300 baud.

  2. Technically the term would not have been “dumb terminal” back in the day. That was reserved for terminals that were attached locally to a mainframe via something like SNA3270 and coax (with BNC connectors) which was a very sophisticated and secure protocol for the time. What you are emulating is a “remote terminal”. Dial-up was as slow as 300 baud and is still available in most areas of USA but at much higher speeds, Not due to the technology of the day but due to the crappy audio a common AT&T POTS (plain old telephone system) had and even worse for acoustic couplers. AC’s were not really for home use as we had direct connect RJ plugs/jacks for our home POTS and remote modem terminals. AC’s were meant for payphones and hotel rooms where it was problematic to get a direct connection that a standard RJ plug and jack would afford you. I guess if your using VOIP you can’t do pulse-dialing either. If you had a POTS like so many Americans still do, it allows for legacy pulse dialing, Today’s dial-up modems can do DTMF easily now.

    The movie you should have showcased was not Back to the Future but this one called WAR GAMES (1983) – it had all kinds of things like slow screens, acoustic couplers, etc.

      1. You are missing stop bits and parity, so on the old systems (1960’s-90’s) like the PDP’s and other terminal based systems, they used Xon-Xoff handshaking, or ReadyToSend/ClearToSend hardware, some just DataTerminalReady (DTR) high/low hardware. One thing about back then is they didn’t have a universal standard. You could guess pretty close, 1 was frame gnd, 2 and 3 were tx/rx, 7 was signal gnd, and usually pin 20 on the connector was DTR. But really, it was all a crap shoot depending on the system. There were many midsize systems that were terminal oriented as well. VT52 standard like a Microbee, or VT100 series for DEC PDP/VAX – before the IBM PC or Apple II+. Others had synchronous communications instead of async for IBM, Burroughs, and Sperry among other – if I remember correctly – LU0 or LU2 (sends a stream or a full screen) when the operator hit the “enter key”. Banks were still using this stuff 10 years ago, and I bet they use it internationally quite a bit still. When the PC came out they started using them as terminals using HLLAPI for synchronous comm, and standard terminal emulation for the others.

    1. Technically TELEX machines were meant for point-to-point text communications not necessarily with a mainframe. That was the job of the ASR-33 TELETYPE machine in 1963. The Friden Flexowriter and the IBM 1050 may have been older. The USN was the first to use them but ideally for point-to-point. The NAZIs had older one made by Siemens in 1940’s. Siemens is still active today. The Siemens & Halske T52, also known as the Geheimfernschreiber (“secret teleprinter”), or Schlüsselfernschreibmaschine (SFM), was a World War II German cipher machine and teleprinter which was better than their ENIGMA machine. The Americans used teleprinters in WWII for RTTY radio teletype. However, the earliest form of primitive landline teleprinters date back to 1849. It was later based on Emile Baudot’s system using a 5 unit (bit?) code in 1874 that is still in use today. Error correction routines are a modern contrivance which only slows down the process. PSK-31 does not use it. Now there is BPSK and QPSK both very good weal signal communication protocols.

      Guess when the first FAX (facsimile) machine was invented? 1843 by Alexander Bain.

      1. I’ve seen output from RTTY that was distorted, it’s worse than any encryption trying to make sense of it :)
        So yeah, error correction is certainly not a mere convenience.
        And especially for wartime communication you want to know you got the right times and coordinates and whatnot.
        But of course before they had IC’s and such or even transistors the error correction circuitry might be a more complex and costly addition. Oh and heavy too, the WW2 military SW radios were 60KG easy for instance, with all those tubes and high power those need.

  3. You can’t send a time machine to your past self because time travel is not theoretically possible, since time doesn’t exist. It’s just a concept for accurately comparing motion to a designated standard of cyclic motion. It’s useful for determining at which point in the earth’s rotation you should drag yourself out of bed in the morning. It’s not a force, or a dimension. If anything you could say it is the endless universal march of entropy. Or better yet an illusion. Things move. We observe all the movements and changes in our environment and buy into the dillusion that there is some universally consistent prime mover thrusting forward all the mechinations of the universe in some uniform fashion. All things in the universe move from higher energy states to lower energy states. To reset the universe to an earlier time, you would have to reverse entropy for the entire universe. Where do you get the energy to do that? Not from this universe or you change the coarse of many things and do not move to the true past. Not from a parallel universe because they are just as rediculous as time travel. Also… how do you orchestrate the reversal of every particles trajectory in the universe so that they return from whence they came? Sci fi writers point to “special” time particles, crystals, flux capacitors, rips in space time (i guess physics is a terrible seamstress?), or just plain magic. Poppycock if you ask me.

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