Teletype Model 19 (and Model 15) Demonstration

We demonstrate our fully restored Model 19 Teletype (from 1940) talking to a Model 15 Teletype (from 1930). This is a demonstration format, from the user operation point of view, to wrap up the restoration. The explanation of how the selector works is new; however, most features were already covered in much more detail as we restored them one by one through many previous videos. The patient folks who learned it all through the restoration process might know most of this already, and much more. And of course Teletype subsidiary of AT&T manufacturing arm Western Electric, not hard disk maker Western Digital... Oh my old brain.

[@CuriousMarc]

Correction: Teletype, subsidiary of Western Electric (not Western Digital!). Modern tongue slip.

[@danielgrenier2417]

Oh Boy! Does this bring back memories... I was a Teletype and Crypto Technician in the Canadian Forces and worked extensively on Teletype Models 14, 15, 19, and 28. I took those suckers apart countless times starting in 1970 till they became obsolete and taken out in the late 70s. Loved working on those far more than on the electronic equipment. I could hear, feel and see the springs, gears, pulleys, levers etc.... All music to my ear I'll tell ya!. I bet I could still fix these given the opportunity. Anyway, thanks for posting. Cheers!

[@Francois_Dupont]

in 1970?!? it seems they would have replaced this with a more simple electro-mecanismt at that point. it is 1930 tech!

[@drlegendre]

The installed base was *huge*, and the .mil is glacially slow to change, in any case. I'm surprised that they were already gone in the late 70s.. wouldn't be the least bit surprised to know they hung around into the early 2Ks. These old models are also insensitive to EMP, another big plus!

[@Tokcat]

This is the most gorgeous piece of technology I have ever seen.

[@BlackEpyon]

And this is why the Enter/Return key has the downward-left arrow. Line feed, then carriage return.

[@lawrencedoliveiro9104]

No, carriage-return first. If you sent the line-feed first, then you still had to wait for the carriage to return to the left before you could send any more output. This is why, on old DEC OSes, the newline sequence could be either CR-LF, or LF-CR-NUL. The NUL was to give the extra time.

[@rattmann36863]

We were taught two carriage returns and one line feed. Air Force. 1970s. Spent many hours on TTY equipment.

[@thayneheath8888]

@@rattmann36863 Yes, I was an operator for US Army in The Vietnam Conflict we were instructed to use two carriage returns and one line feed. I don't recall the exact technical reason for that, but had to do with retrieving and restoring data on the tape should you fail to enter a line feed or return command.

[@HappyBeezerStudios]

And different text editors still use some of it. Stuff like the C64 or Speccy used only CR, Unixoid systems like Linux, BSD or macOS use LF and Windows expects CR LF. In case you open a file and the standard windows text editor doesn't do new lines properly

[@davidhollis1117]

My Grandmother worked as a dispatcher on the railroad in and I can remember the smell of the ink and lubricants used on these machines from when we would visit her briefly at work in the early 70s

[@wjcroft72]

Quite a restoration, to go from rusted teletypes to cleaned, oiled, and it looks like you repainted the cases as well, amazing. I worked with the Model 15 in the late 1960's at ham radio station W9YB at Purdue University. Built and installed the small box which converted the audio tones (FSK frequency shift keying), used "on the air", to relay pulses driving the Model 15. Later at the Electrical Engineering Department, used a Model 35 KSR teletype as the main console on the DEC PDP-9/339 "personal computer" in the Graphics Lab. This was an amazing experience to have this type of gear at that time frame. The PDP-9 had an enormous "radar tube" type display and a light-pen for input of commands.

[@CuriousMarc]

Yes, good old RTTY, teletype over radio! We have an original RTTY tube tone decoder from the 1950's, so that's what we want to do next with this TTY. See the PDP-1 video for the "radar" terminal with the optics pickup: kzbin.info/www/bejne/Z3a6gox3m9qAj9k . Very much ahead of the times!

[@MikeKobb]

I can't believe I've spent as much time watching videos about Teletypes as I have, but darned if they aren't fascinating! Thank you!

[@James_Knott]

Many years ago, I was a technician with CN Telecommunications in Canada, working on model 28, 32, 33 & 35 Teletypes. The models 15 & 19 mostly predated me, but I did manage to acquire one one of each, which I had planned to connect to my amateur radio. I never did with those machines, but did so later with a M35, which was connected to my IMSAI 8080 computer. I don't know about the 15 & 19, but later models had an option where a single character would do both CR and LF. One thing about these machines is the clutches. You can see one spinning near the selector. These clutches were simply flat metal disks, with an oiled felt between them. When the clutch was released, the friction from the felt was all that drove the mechanism. These machines also required a lot of oiling the various felts and not just the clutches. There was a variation of these machines, made by Lorenz in Germany, which were often found in Telex service. Also, Western Digital is an IC manufacturer. Teletype Corp. was owned by Western Electric. BTW, back in those days I had the Baudot code memorized, as I used it so often in my work. Incidentally, upper case only predates Teletypes. Morse code didn't have lower case either.

[@Tigertony67]

My father was a teletype operator for many years for UPI. I remember going to work with him all the time when I could, thanks for the memories. Fascinating machinery.

[@umageddon]

The old television news programs where all you would hear in the background was the TTY machines running receiving the news feeds. That steady, monotonous rhythm can be heard even in todays news ‘musical’ intros

[@thiesenf]

The sound effects used in the movie "Alien" where "Mother" is typing out text actually is a combination of teleprinters and other sounds IIRC

[@lawrencedoliveiro9104]

I remember a bunch of machines in the newsroom where my father worked. Looking at pictures online more recently, I believe they were Creed machines. Just hearing the noise brings the smell of hot metal and that ink ribbon back ...

[@ianleitch9960]

@@lawrencedoliveiro9104 Yes, Creed & Co were UK Teleprinter manufacturers. I used them extensively in my RAF career in the period from 1964 through 1983, before I moved into computer operations. 7B, 7BRP, 85R and various tape transmitters. A great time.

[@markevans2294]

Likely the Model 28. Given that these were orginally designed for the US military they may be literally "bomb proof". There's also the IBM 2741. A derivative of their Selectric typewriter. Notable for it's type/golf ball printhead.

[@jamespfitz]

Old? 😭 We used these in college journalism class for AP & UPI wore copy in 1985.

[@andie_pants]

I imagine an elder IT nerd watching this video, tears streaming down their face as they see their beautiful baby brought back to life just as they remember it.

[@andie_pants]

... or else an embittered old Teletype repair tech suffering a shock of PTSD going "OH MY GOD HE RESURRECTED THEM FROM HELL!!"

[@Omnihil777]

Just WOW! I'm collecting mechanical calculators and this is taking the mechanical linking tech on a whole new level (although you can find the cousins and grandpas of these linkages in there too). My mind was just blown a few times, need a BIT of time now. Wow! Thank you for these videos, seriously, DON'T STOP making them.

[@TheSonicfrog]

As a one-time troubleshooting technician and ex-Navy computer operator (Univac AN/YUK 5V built out of transistors, core memory, tape drives, printer, card punch/read with Model 33 Teletype as console) I love how you go through every troubleshooting step in detail, not to speak of your excellent persistence in resolving issues! Well done!

[@andie_pants]

This series on the teletype has given me a profound sense of nostalgia for an era that I'm way too young to have known. What a fantastic ride it's been so far!

[@michaelcherry8952]

Congratulations! I thoroughly enjoyed these videos. Thank you so much for taking us through the restorations in the various episodes. It's amazing to think that something so utterly, proudly mechanical was also so very reliable and ubiquitous. Every news outlet, big or small, had at least one Teletype. Government agencies used them. The military and police used them. Businesses large and small used them. And they worked very well, sometimes under difficult circumstances. It's so great that you and your colleagues put in so much time and effort to revive these machines. Bravo!

[@richardhaas39]

A Polish nuclear physicist told me that they were also used east of the Iron Curtain.

[@drlegendre]

@richardhaas Like all other Western tech, the Com-Bloc nations ripped these off too.

[@raywood8187]

Thank you, Marc! It's great to finally put a face to the sound that used to accompany evening news broadcasts in the 60's and 70's. I was reminded of this very recently while watching the Apollo 11 mission replayed in a live KZbin channel, seeing old news broadcasts with TTY sound in the background. Some things are worth preserving and this is one of them, a monument to pure mechanical ingenuity.

[@anotheral]

I would love high quality audio samples. Thank you for sharing this - as a long-time linux sysadmin, I love the rich history of our ecosystem.

[@fishermanfrank4522]

Arthur Henry Phillips was a Supervisor in the Central Telegraph Office till 1934 and worked with Baudot and Murray-Creed machines. Amazed at what my Uncle did with this sophisticated and very complex electro-mechanical equipment. This increased my respect for people like him!

[@TheFunkman]

After 60+ years of electrical and electronic experience, I learned something! Thank you.

[@compu85]

I'm still impressed with the printing quality of these teletypes. Most I've seen are half out of ink, type bars full of junk so the circles in the characters don't print properly, and the characters don't line up properly.

[@CuriousMarc]

Good observation. There sure was a lot of typebar bending behind the scenes to get the characters re-aligned properly!

[@drlegendre]

@compu85 These machines use the (once) heavily standardized Royal spool ink ribbons. They're still available, inexpensively - no such set should ever be low on ink. The original ribbons were pure silk, and could be re-inked many times.

[@andrewrixon2347]

Thank you yet again Marc. Your previous restorations kept me going whilst I was off work with multiple kidney stones. Now I’m kind of well and back to work, your videos set me up for the day ahead. Thank you again. Joyeux Noel !

[@MattTester]

I watched every restoration video but I'm still blown away by the engineering that went in to these machines. You've all done a superb job in restoring these.

[@w9gb]

Read the history of Edward Ernst Kleinschmidt, one of the inventors of the teleprinter. He sold his first company (Teletype Corp.) to Western Electric (division of AT&T) in 1930 for $30 million in AT&T stock. His follow-up company (1931) still exists today. en.m.wikipedia.org/wiki/Kleinschmidt_Inc I met his grandson, several years ago

[@andyt.4124]

Way before my time but what a cool video to watch. Amazing piece of machinery and even more amazing how you are able to understand and restore it.

[@roelbrook7559]

There's so much recognizable stuff in these machines that persists to this day. Such as the CR & LF for Windows (pointed out in the video), but also the 80 character limit on the (default) Unix terminal. This is very cool to see.

Thanks Marc. This video is historically invaluable for posterity!

[@525Lines]

You'll make all your money back the first time a movie crew wants to rent this equipment.

[@w9gb]

You missed the KZbin video about “The Rum Diary” kzbin.info/www/bejne/pIitmn-ifb91b80

[@Milosz_Ostrow]

Even more money hiring oneself out as a technical consultant to operate the equipment during a shoot.

[@jasonsaboury3227]

You know any movie crews?

[@525Lines]

@@jasonsaboury3227 How do you promote your services to the movie industry? Good question and one worth investigating.

[@julianadams5753]

As a young man back in the early 1960s I remember watching one of these beasts in a North Carolina radio station hammering away at over 100 WPM receiving a news feed from one of the wire services. Quite an entertaining experience it was!

[@GeeWillikersMan]

Thank you. For all of this.

[@bluesky940]

I know, right? Im loving these videos!

[@jamesbrewer3020]

Thanks. I know this is years late but great video. I had a Model 15, 19, 28 ASR and two Kleinschmidt 100 wpm Teletype Sets. Used them almost every day for many years copying incomeing traffic for Navy MARS. Loved that sound and smell, nothing like it.

[@JBiggsNewJersey]

Who thinks of this stuff? The engineers should be very proud. Great video.

[@OO-qd7fh]

This is sick!, This is GOLD! The level of abstraction nowadays is staggering!

[@arjovenzia]

Just... Awesome. Inspiration of Awe. Ive always loved RTTY, and read alot about it. But this is the first time i feel ive actually understood how the machines worked. So much easier to understand when you can see each bit running. All the theory falls into place. Beautiful, just beautiful. Many Thanks

[@wessmith2112]

Binge watched the entire series last night! This is awesome!

[@REVENGER166]

Very nostalgic . I was a radio/teletype ( 31c) in the U.S army .

[@tdiddle8950]

Great vid. Fascinating. Such an extraordinary world we live in where people can be into such niche things.

[@Cow-Moth-With-A-CRT-Head]

There's something special about seeing how things like this were done in the past. Really cool to see these machines in action!

[@russellhltn1396]

I'm not sure as this has been covered, but the idea behind the signal loop is that you could have any number of keyboards, tape readers and printers. Any could send (one at a time), and all would receive. No real coordination about who is going to send is required since anyone can interrupt the loop to send. The current loop meant you didn't have to worry (as much) about the voltage drop across long lines. 60mA (or 20mA) is the same everywhere in the loop. Short distance, long distance, it just works.

[@jlscott64]

And the bell was used to signal other operators. I once read someone's recollection of finding out JFK had been assassinated. I think he worked in a small newsroom somewhere. The press teletype rang 10 times, which meant the highest priority. The teletype starting printing news of the assassination. Someone else started typing something else, so the bell rang 10 more times to shut him up and then the report started over.

[@BilalHeuser1]

It's really interesting to note here that Unix was designed to work with teletypes (TTY) and quite interesting to see a real teletype in operation today. Thanks!!

[@wjcroft72]

Yes, Ken Thompson and Dennis Ritchie used Model 33 Teletypes, the least expensive at that time. These were the console I/O used by DEC computers of that era. Unix began on the PDP-7, then moved to the PDP-11.

[@jimmcdonald9244]

Wonderful documentation and restoration work Marc, thank you for publishing

[@TheSaltyBalls]

Some of histories greatest electric machines preserved on your channel with hardly any views... most underrated channel I’ve ever seen. Your production quality is leagues above what KZbin deserves. Thank you.

[@Shipwright1918]

Recently acquired a Model 15 myself in full working order from a ham radio operator. At present, I'm trying to get some hardware that will allow the teletype to communicate with other machines via the internet and the auspices of the I-Telex hobbyist group, but I admit I'd be equally happy just to have the machine operate locally (.i.e. talk to itself) to demonstrate it and maybe use as an overgrown typewriter.

[@vincei4252]

Thanks for this, Marc. Excellent recap. My dad had a Telex machine in his office in the mid 70's thru very early 80's The racket brings back the memories and the amazement of receiving messages from abroad right into the comfort of you own office! :-)

[@martinbarry62]

I have followed this restoration project just about from the beginning. Very enjoyable and educational. I used to know technicians who fixed these at a wire service. They're long gone now.

[@gnored]

I have really enjoyed watching the process of restoration, and it is now really fun to see the finished, and absolutely perfect, machine working. Thanks for this video.

[@Mrcaffinebean]

That was incredible! Thank you for the detailed video and amazing restoration work! The all mechanical nature of this machine is really something to behold. The minds that conceived it were clearly on another level than a person like myself.

[@WyomingGuy876]

What a gorgeous machine; applaud your efforts in the restoration.

[@jim671671]

Thankyou to everyone involved in restoring these beautiful machines. Would love to find some one day. The birth of binary!

[@AlexisKasperavicius]

I watched all of your videos on this restoration here in dark, wintery Berlin over a couple of days. Thank you very much for making them!

[@Wok_Agenda]

I was hearing stories from old grandpas in my father's birthplace which is in rural Greece, they left that part of the world and migrated to the US in the late 40s and they say it was like going 50 years to the future. Imagine leaving a place without electricity without any car and go to a place and see all this wow man...

[@dindinumairdegouliwi]

Incredible videos. Fantastic resurection. Power supply has something worrisome with theses colored valves. Thanks for videos. And thanks for your accent who allowed me to understand clearly all problems you met. A french suscriber with a bad english spoken... :-)

[@alainmulaire9471]

très impressionant Marc! merci

[@MikeBramm]

Beautiful demonstration. Pretty ingenious how they figured this all out back in the 1930's.

[@lernik4]

wow, this is superinformative!! thanks a lot for such a great video explanation!!

[@bluesky940]

Thank you for all the work you put into making these videos. It's been a joy to watch them today. I cant wait for my dad to see this one. We love this stuff!

[@briansmith8967]

Amazing demonstration and restoration, by the way!

[@cyberp0et]

Fascinating machines!

[@NathanOkun]

The later ASCI 7-bit code Teletypes had printing upper and lower case characters and a combined carriage-return/line-feed single character input/output, as well as a number of other special non-printing characters. The printer head on the ones I am familiar with used with the early US Navy digital computers on warships was a moving block that used dots to form each printing character at up to 10 characters/second. When I ran the TERRIER GMFCS in-house simulator at what is now called NSWC/Port Hueneme Division, which was used for checking out bugs, writing code patch corrections and small updates (large changes were done by a contractor), and testing the new version of programs before sending them to ships, I used a Teletype for most manual command inputs and printed outputs, though eventually heavy, Military Specification (waterproof, "Sailor-proof" :-D, etc.) CRT consoles replaced them (not everywhere in our test simulators, though, since our motto was "if it ain't broke, don't fix it" and we used some Teletypes in-house to the very end of TERRIER in 1992). The chattering of Teletypes was a major part of my life for many years...

[@w9gb]

Nathan - Kleinschmidt 100-words-per-minute typebar page printer was made the standard for the Military in late 1940s. en.m.wikipedia.org/wiki/Kleinschmidt_Inc His first company, Teletype Corp. was sold to Western Electric/AT&T in 1930 (typewriter-style mechanical printer). == The dot-matrix printers were around for four decades, before their application usage became serious. IBM, OKI, and DEC early mfg. I used a “then new” DEC LA36 DECwriter II while in college. en.m.wikipedia.org/wiki/Dot_matrix_printing

[@NathanOkun]

@@w9gb Another minor point that I found when doing my patch/update work was that the original printer output code used with the US Navy Mark 152 General Purpose Digital Computers made by UNIVAC (a Sperry Corporation sub-section) for the TERRIER missile fire-control systems -- as big as a large double refrigerator and with its front covered with flashing lights (a STAR TREK/STAR WARS movie computer if there ever was one!) -- software assemblers (no compilers since the machines had too small memories for anything but assembly/machine language coding) originally used at NSWC/Dahlgren Division (the old US Naval Proving Ground from which we inherited the TERRIER software) was still on the original PUNCHED CARDS!!! We immediately did a very tedious process of changing all of the cards onto magnetic tape and extensively updating the software to use more modern input/output equipment, such as better high-speed line printers, TEKTRONIX Corp. CRT consoles -- the same ones used in the original BATTLESTAR GALACTICA TV Show (!!!) -- for the simulator operator control consoles (Dahlgren had used old obsolete radar-CRT-equipped fire-control consoles jury-rigged with all sorts of kludges for their control consoles), and so forth. When doing this we found that the assembler software, TRIM III used exclusively by the Mk 152 and a few similar UNIVAC machines, had been built using a Type 26 IBM card reader/printer, not the later IBM Type 29, which replaced Mk 26 almost everywhere. The Type 26 seems to have been developed when the original Teletypes were still using the 5-bit I/O system, not the later universal 7-bit ASCI Teletype machines actually used with our computers. Because of this, there were a number of standard English language characters (double quote marks, for example) that I could not print out on the Teletype or on the line-printer when doing my work with changing any of the programs I used, in-house and for the ships. I thus had to use somewhat convoluted sentences in my printouts when writing them during work with the machines, which irritated me CONSIDERABLY! Eventually I could not stand it anymore. I dug into the TRIM III Source Code and found the tables where it created the printer outputs and by hand built a patch the added all of the Type 29 IBM card reader/printer full ASCI character set to the assembler's character source buffer (now using virtually every English character) and generated the modified TRIM III computer machine code to read them from that table. I then created an entirely new set of tapes with MY unique superior update to TRIM III and used it from then on until TERRIER went away a few years later. It was a nit-picking thing to do, but I am a perfectionist and I used the task to learn more about how TRIM III worked. Sometimes I think that I'm crazy when it comes to doing things right, no matter how much extra effort it takes...

[@nickengland]

Actually the US Navy had only a very few Kleinschmidt machines - they used tens of thousands of Teletype Corp. Model 28 machines, while the US Army went with Kleinschmidt.

[@w9gb]

Nick - Sadly the Teletype Buildings in Skokie are gone (demolished in early 1990s). Last building was converted to a Parking garage ! Kleinschmidt still exists in Deerfield, IL ... (after splitting from Smith Corona) but now working with EDI and other business lines.

[@richardhaas39]

@@nickengland I believe the 28 was developed with the Navy in mind. The large carriage of the 15 and 19 respectively were impractical in rolling seas.

[@maxpetrelli2142]

Awesome job! Truly a masterpiece of electromechanical engineering. Please keep going with other restoration project ;)

[@daviddavidson1372]

Beautiful machines. What an amazing restoration you did on these.

[@samuelsmith393]

This brought back my memories when I served in the signal corps,,,O5C,,,thanks much

[@SusanAmberBruce]

So good to see this old stuff working, thanks

[@dwagner6]

This is an amazing cumulation of the whole series on your restoration. Thank you for sharing this!

[@lordskeletorde]

This is fascinating. Great video!

[@jrmcferren]

The separate carriage return and line feed reminds me of the typewriter my great grandmother used to have. The carriage return arm was broken so what you had to do was return the carriage and turn the knob two clicks (as you may recall each click of the line space ratchet is ½ line). I eventually inherited the machine, but unfortunately I killed the draw band (somehow I had a round of bad luck in my teens with typewriters where I kept breaking draw bands). I'd love to have a few teletypes, but unfortunately I'm not that good with mechanical devices. In fact the closest I've ever been to working with a teletype was actually a DEC LA-120. For those not familiar with that, it is a dot matrix printing terminal, but it shares more features with a CRT terminal than a TTY. I originally was tasked with troubleshooting it remotely, but I ended up where it was (600 miles away) after they tried a few hacks to fix it. Fixed the hacks, advanced the ribbon to a good spot and then started getting it to reset on the characters. Long story short, 600 miles, several unrelated shots in the dark and it was the electrolytic capacitors in the power supply. Put it on the capacitor tester and they were most certainly failed (a good capacitor would have been out of range on the tester and they actually measured), of course I also knew that from the printouts and seeing one of the main power rails dip 50% (when I finally got it on a scope) when it crashed .

[@akb168]

Really liked the summary you put at the end for 32 seconds starting @ 21:22 for end to end data transmission between the two machines. Great job!

[@andiarrohnds5163]

oh Marc these videos are so wonderful

[@unbiased1]

Very nice toy. Loved the video.

[@Stelios.Posantzis]

Finally got to know what carriage return and line feed actually stand for! About time too!

[@projectartichoke]

I had one of these back in the 1980s for radio teletype (RTTY) amature radio listening. I think I paid $15 for it. Wonderfully engineered and built like a tank. A truly amazing machine. I just had to build a simple demodulator circuit to connect the radio receiver to two electromagnets in the TTY unit.

[@randalltufts3321]

Nice demo guys. Great video 👍

[@billmoran3812]

In the 60’s I did Radio Teletype with Navy Mars using a machine loaned to me by the navy. My ch later I was in the Coast Guard and we had two teletypes in the group comm center. One was with District command and one was to message ships for which we had communication guard. We often made punched tape of messages from district that we had to retransmit to the ships. We would take the tape from one machine and run it into the other machine so as we were receiving it, the message was going back out the other loop.

[@HailAnts]

I am totally geeking out right now!!

[@RapperBC]

BT ABSOLUTELY BRILLIANT - THANK YOU SO MUCH EOT

[@markevans2294]

The Teletype Model 20 used the six bit Teletypesetter code (TTS), which does support both upper and lower case letters. With a tape punched by one of these being able to be fed to a Linotype machine.

[@memeboisvert7907]

I actually used one of these at my first job in 1980!

[@valeinikofff]

great! reminds me of my younger days. thank you!

[@Regular6782]

This is amazing! Thank you!

[@gloriaangelicacorona5366]

Magnific! Thanks for sharing! 🙂

[@rogerm8557]

Very nice Marc! I believe these same machines were used in the early days of Radio Teletype (RTTY). It was the only equipment available for sending and printing. Of course, they were modified to include FSK modulators and demodulators. We still use the 5 bit Baudot code in ham radio RTTY today!

[@CuriousMarc]

RTTY was sure a very popular application for 5-bit 45.5 bauds teletypes, for a very long time. Army and Navy were big users. Weather stations still transmitt at 45.5 bauds. There are a few hams that use real teletypes rather than emulated ones.

[@rogerm8557]

@@CuriousMarc Yes, there are a few hams that still use true FSK for RTTY. But, with the proliferation of PC based and external sound card devices, Audio FSK (AFSK) is most often used now.

[@funksterdotorg]

Fascinating! Thank you for making this :o)

[@zacksargent]

It's crazy that, even though this is so complicated, it's very easy to understand compared to the computers we use every day.

[@dangoldbach6570]

Wow. Just... wow! I had no idea how complicated these machines actually were. You can almost see the birth of digital code and how it gradually becomes the foundation of computer code. The swords are like mechanical versions of flipflop memory circuits! I can't help but think the people who designed these would immediately recognize their architecture if they were to look at computers in the present day and how they work. Awesome job restoring this very cool machine!

[@w9gb]

Mechanical Engineering. Go see Union Pacific 4014 “Big Boy” steam locomotive for 150th anniversary of Transcontinental Railroad completion. Pinnacle of steam locomotive design in 1940s.

[@mikecowen6507]

Dan Goldbach Not so much flip flop *memory*, but real-time, *mechanical* parallel to serial, and serial to parallel conversion. I often point out the lineage of the telegraph to the internet. TTY lies somewhere in the middle. It blows the "young 'uns" away. In WWII, they were using automated *analog* computers to route *digital* TTY messages! Of course, now it's practically all bits, except for the glaring exception of radio distribution (RTTY, cell phones, digital TV/cable, etc., or even fiber). As you cannot transmit a steady state voltage through the air (or fiber), it's sent as a modulated carrier (aka: analog), even if the "message" is in a digital form. Funny how that works...

[@w9gb]

Mike Cowen - My retired mentor (IL EE late 1950s) pointed that out to every RF engineer. A couple of classes ahead of him was Bill Henry, who would become co-founder of HAL Communications that developed RTTY ST-5 demodulator and numerous developments including original AMTOR/PACTOR.

[@craigmichael19]

So cool, thank you for sharing!

[@coles201]

This really is very amazing.

[@JacobJonesy]

Marc after all this time you just blew my mind, I learned VB6 when I was a kid and always took CrLf for granted as a weird way of saying Newline. Now it makes sense!

[@rty1955]

You need to send the CR THEN the LF. If you did it backwards, you might either get a jamb or a character printed WHILE the carriage was returning

[@RaymondHng]

22:10 "This is the _CBS Evening News_ ...with Walter Cronkite"

[@VenturiLife]

We had one for a while from Telecom Australia. These would have been state-of-the-art once upon a time.

[@ghostindamachine]

Incredible!

[@TheFunkman]

What genius design!

[@SuperBowser87]

Very impressive!!!

[@markevans2294]

The ASCII DEL code is also "punch all" with 7 bits. In addition to 5 and 8 hole 6, 7 and 9 hole tapes (possibly others) were also used.

[@stevenbennett3805]

In the 5 bit Baudot code the presence of signal is called a 'Mark' and the absence of signal is called a 'Space'. These Marks and Spaces are recognized when they occur within the span of time between the Start and Stop portions of the 5 bit signal. There was a time when I could reassemble a completely stripped down Model 28 ASR printer and keyboard, including the complete reassembling of the main shaft and have it adjusted well enough to operate at a minimal range. Old techs will know what that means. Here's to bell cranks, code bar bails, function boxes, and dash pots with the occasional 60ma zap.

[@WickedScott]

It's sad to think such marvels of mechanical engineering didn't have a longer time. I imagined things like this would be like the tech in Warhammer 40k. Handed down generation after generation.

[@davidbarts6144]

Separate CR and LF characters were done because the mechanical motions required to implement both took so long that a TTY wouldn't have time to do both motions before the next character came in. Splitting up the task into two separate motions, each with a dedicated control character, got around that problem.

[@Pants4096]

Such a fantastic video! Thank you! And since this is the internet, your adoring fans can post their demands (requests? polite suggestions?): Slow motion! Most smartphones can do 240fps video recording, or if you could get ahold of a 1000fps that'd be even better, it would be SO cool to see the mechanism decoding slowed down so we can see ~ one bit per second. (This is 45 baud, right? so you'd need 1,350 frames per second slowed down to 30fps.) My other burning questions: How did the receiver synchronize off the start bit. It had to be ready to start decoding EXACTLY 1/45th of a second after the start bit began. How did they do that, mechanically!? When sending without typing to tape first (how fast could you type to tape?) what was the user experience like when you tried to type faster than it could send? Would you simply not be able to press the next key until the previous one had finished sending? 1930. That breaks my mind. Such an amazing technological achievement. Thank you again!

[@CuriousMarc]

Receiver sync: it's done by the start mechanism / range finder. It's a very smart mechanism that releases a friction clutch very precisely, worth a video by itself. This very mechanism does not work at first on my model 19 in episode 8, so I take apart some of it (right about here kzbin.info/www/bejne/ZoTKeoCAhdOMhs0) . The part you see me clean is the range finder, which adjusts how long it takes before the clutch is triggered. Unfortunately I do not show how it controls the clutch finger which stays on the machine. When typing too fast: I have to check - but it's too late and it would wake up the whole family. I can't remember if you can't press the key, or if it just does not respond to it.

[@mumiemonstret]

@@CuriousMarc That sound would be the best thing to wake up to!

[@CuriousMarc]

@weildish Nice filming, particularly the first one!

[@JuliaVikulina]

There is a buffer where the tape is collected before being sent, it's about 14 min in the video

[@MildMisanthropeMaybeMassive]

Maybe contact to Slow Mo guys to see it they’re interested.

[@GeneralGuts1]

Amazing this was around 1930's

[@AlainHubert]

Wow indeed. Being an industrial mechanic myself, I can appreciate the level of complexity of such beautiful machines. One question came to mind when watching this: what would happen if the operator types faster than the transmitting speed in send/receive mode ? Is there some kind of mechanical buffer in this system ? Or would using the tape recording method (tape mode only) be more appropriate for such speedy typists perhaps, to send at a later date ? Can't help but be reminded of IBM's Selectric typewriter, which came much later, which also used encoded digital data to move its "golf ball" typing head. Another marvel of human engineering. Anyway, a very interesting video (as always), and merci beaucoup Marc for sharing it !

[@CuriousMarc]

There is an interlock. You can't type faster than the 45.5 bauds of the machine when in transmit mode (switch on Keyboard or Tape & Keyboard). But you can if you are in the Tape only mode. Then you can theoretically type faster (you have to be really good - I can't really do it). That's the main purpose of that mode. Then you thread the tape directly out from the punch into the transmitter as I show, and let the extra tape loop through the hole on the table. Then if you do really well and get ahead of the transmitter, you can go take a coffee while the transmitter continues to transmit the remaining tape.

[@andie_pants]

@@CuriousMarc The world seriously needs more people like you, Marc.

[@PappyGunn]

This is one reason for the QWERTY keyboard, to slow down operators with a layout that doesn't make senses.

[@thayneheath8888]

I was a teletype operator in US Army. The older machines were set to run at 60 wpm. The machines I used were 90 wpm capable. You could not over type in speed the machines

[@drlegendre]

@pappygunn Only at first. Soon enough, muscle memory will learn any keyboard layout.. regardless of order.

[@Milosz_Ostrow]

I find it interesting that the typeface of the Model 15 and Model 19 appears to be identical to that used on the Model 35, even though the machine designs were separated by decades.

[@izzard]

Beautiful machine(s)! Thank you for showing them in detail and explaining them so well. I have one little suggestion/request for your next video of this type: could you perhaps get something like a lapel mic so your voice is more distinct over the noise of the machinery? I'm really enjoying your videos - thank you for putting them out there.

[@ypey1]

Internet 1.0 right there! great to see, amazing machinework