Friden STW 10 Mechanical Calculator Demo

Yes, this 1956 Friden STW10 is the calculator machine on the desk of Katherine Johnson in the movie Hidden Figures. Let's try it out, it's way more impressive than in the movie (I suspect theirs didn't work fully). If you want a fun demo that's less of lecture, see the "dividing by zero" video instead: • Divide by Zero on the ...
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[@leokrupp4442]

Ah the good old days when your calculator needed an oil change every 3000 calculations or 3 months, which ever comes first.

[@puppiesarepower3682]

To be fair, you didn't have to worry over a busted ECM, BCM or PCM.

[@bwhog]

@@puppiesarepower3682But when your calculator crashed, instead of just throwing an error, it might throw parts all over the room! 🤣

[@mikeklaene4359]

The department store at which I worked in Cincinnati back in the late 60's had a room full of these machines in the statistics department. The ladies who used these machines were amazing to watch.

[@hiboabdi5887]

Send one to me

[@bill605able]

The engineers in my college had a room full of these and someone set them all to divide by a zero and ran till their motors burned out on a weekend whe nobody was there.

[@davecrupel2817]

@@bill605able what an asshole.

[@robinbennett1430]

That room full of girls would have been comptometer operators using comptometer machines.

[@GRBtutorials]

@@bill605able So... did it catch fire?

[@PanduPoluan]

The NOISE of that machine OMG... This machine WILL survive an EMP pulse, though 😁

[@lowercherty]

Imagine an office full of them. My dad was a corporate accountant in the 50s and 60s and this is what they had. He saw the first electronic calculators about 1970. He was near deaf when he retired.

[@JohnSmith-eo5sp]

It has an electric motor

[@AttilaAsztalos]

EVERYTHING that happened to be inside a suitable Faraday cage (=metal box) and disconnected from mains power (=physical switch at the back -> off) at the time will survive an EMP pulse, though.

[@randywatson8347]

Must have been insane to design this device.

[@SergeantExtreme]

@Juden Arier Correction: We had the greatest *mechanical* engineers. Japan actually had the greatest *electronic* engineers. In fact, Japan put 3/4th of American mechanical manufacturing businesses out of business (including the Friden Corporation whose product is featured in this video) because they failed to be able to create electronic devices as good as the Japanese devices.

[@WDF1500]

The mechanism itself is not very complicated, it is just the mechanical equivalent of logic modules of simple ALU from processors. From the service diagram, you can learn that the user simply controls the clutches that activate the sequencers that direct the motor's outlets to specific rotors. However, due to miniaturization, packing into a small housing and maximum saving of electronics, it is very difficult to understand what each element in this device does. It would be easier to design something similar from scratch than reverse engineering. I think that today's processors are much more complicated. It does not change the fact that to design it without cad, and to produce it massively in 50s had to be a good feat.

[@helmut666kohl]

@@WDF1500 Yeah a CPU is way more complicated, but also offers a dozen layers of abstraction to deal with it. Hard to create a simplifying overlay for a mechanical machine… :-)

[@false404]

@@helmut666kohl This device kind of *is* the simplifying overlay! Haha

[@2adamast]

The layout follows a standard. I have a 'simpler' purely mechanical model build decenia earlier somewhere else, it has a similar size and when present the buttons are at the same place.

[@hotpockets2224]

I came here after seeing your divide by 0 video. Its a really cool machine and I wanted to learn more about it thanks

[@mitchm5049]

hotpockets222 same lol

[@josejj2893]

Igualmente

[@feliperout]

Me too!!

[@smuwu21]

same

[@robinbennett1430]

I actually worked with one of these machines back in 1963 in my very first office job. I was trained only to do addition. But after completing a routine addition job, i was curious to see what entering dividend and divisor and pressing the two division buttons would do. Unfortunately i was on a small desk with high cabinets on either side. I pressed the two division buttons and the monstrous machine burst into life. The rear carraige hit the right hand cabinet first and made a terrible sound. Then the rear carraige careened leftwards and smashed into the left hand cabinet, again groaning like a dinosaur taken down by an elephant gun. The rear carraige centralised and just kept on groaning terribly. My boss rushed over to his pride and joy and eventually pulled the plug out of the socket and the whole office of 40 people went deathly quiet. All you could hear was the internal clink clink of cogs and wheels as they dropped out of position and onto the floor of the machine. My boss politely asked me to take a walk through the factory for an hour or so. I never saw a working Friden ever again.

[@viperRX]

Hahaha. And by the way that is 58 years ago wow

[@ahmadjarrad2635]

Did you get to keep your job though?

[@robinbennett1430]

@@ahmadjarrad2635 yes i was a commercial apprentice for a further 3 years. Then i got a job as a trainee manager with a chain store in Liverpool. But i was unable to stop myself from breaking rule 18 and returned to life as a student.

[@puppiesarepower3682]

Wow Robin that was a big oopsie. But it shows that no matter how bad one's day is there will always be a person who has it worse. 🤯

[@oakridgehighschoolmanufact7655]

My grandfather worked at Friden and worked in the engineering department as a Manufacturing engineer. He had a lot of stories about it and the challenges of getting the mechanical components to reliably interface. He had kept some frame parts and gears that didn't meet specification. I will have to see if any of those items survived in his estate.

[@thearousedeunuch]

Did those items survive?

[@ryuucld384]

Oh, this takes me back quite a few decades! In the 1960's, my dad used to work for Friden as a repair technician and continued on after they were bought up by Sears for several years. This was one of the devices that he was qualified to work on. Such a fantastic machine, too! He had one that he brought home "to repair"--and it stayed for years officially "still under repair". I don't know if that thing ever did get returned. LOL! My brother and I used to play with it for hours and days, putting it through some serious paces, and it was just as much fun watching it do the calculations as it was to finally get the answers we were seeking. Oh, and *minimum safe operating space* for that damned thing is most assuredly 3x it's width!! I grew up to love doing mathematics, and later electronics, computers, and now I'm playing full time with CGI. This device was most certainly one of the early seeds that got planted into my heart. Thank you for posting this video and giving me a look back to the source of so much joy!😁

[@kleinfeicht]

Student:"can I use any Calculater at thd test" Techer:"Yes" Student open a bag and put that thing out.... then he calculate and everyone is looking at that noise machine

[@nigelft]

There is a video of a student turning up to a large lecture, with a portable typewriter ... As soon as the professor started talking, and the student started two-funger typing, he was swiftly ordered out by said professor ...

[@paulondra19]

I just saw Jack Lemmon use one of these in the movie "The Apartment" and I wondered how it worked. Now I know! Thanks!!

[@CuriousMarc]

+Paul John Indeed! Here is a short scene on KZbin, he crosses a room where there are maybe hundreds of them! kzbin.info/www/bejne/rmSYZ5-iaM2Hrsk

[@hopeisneversilent]

I'm watching "The Apartment" right now! I had to know what the heck they were doing, so glad I clicked. 😀

[@KevinEontrainer381]

13:18 NEIN NEIN NEIN NEIN NEIN!!

[@2312micha]

OH! OH! OH! OH! OH!

[@zarax3904]

😂😂

[@roachtoasties]

When I attended Chatsworth High School (CA), they still had machines like that in Business Machines class, even though there was no bank in town still using them. There were also desktop electronic calculators in the same class. During assignments and tests all the students had to rotate though the machines (there were about 40 machines with close to that many students). I kind of did a shortcut, and said the heck with trying to do math problems on the old Fridens and other machines. When I got to the electronic calculator I would do all the assignments as quickly as I could there.

[@charlie_nolan]

Until clicking on this video today, I never knew there was a such thing as a mechanical calculator. This is amazing

[@dizzolve]

I noticed one of these machines on the desk of the computer on that movie 'Hidden Figures' and was curious what it was. That thing is really something else! It's amazing what was built back in the day

[@ffggddss]

Yes, I recall using one similar to this one, that was in my dad's office at the Weather Bureau, when I was a kid in the 50's. It was big fun! Fred

[@The_Real_Chris]

I recently completed a complex full rebuild of a Sweda 46 cash register. Have been looking for the next challenge and came across this video last week while perusing your videos . I fell in love with the STW 10 and have watched all your videos on the subject. So today I’m out and decided to stop in the local antique store. Buried under a stack of furniture and an other junk was a STW 10. The owner told me it’s been there for over a year. I couldn’t believe my luck. Plugged it in and it buzzed and immediately jammed. I was never so happy...now I have an excuse to carefully work through it and hopefully have a working machine within a few weeks or months. I just wanted to thank you for uploading the documents and making these videos. Sweda documentation is non existent and nobody has a copy of anything. The Sweda 46 restoration was 4 years of trial and error to get timing and all the tiny mechanics working just right. Starting a new project with actual service documentation takes a huge load off my anxiety. This may be an old video...but it’s all new for me.

[@bishopworks3203]

This is really amazing, its very impressive even today!

[@csegura26]

10 of that calculators working simultaneously had to be a mess....

[@christinetaylor2427]

I used the Friedan in 1962 while working in the offices of C&A in Marble Arch. I remember the invoice prices had to converted to decimals. We had a card with the decimal conversions that we could refer to but it was quickly learned. With at least 20 or more of these machines going at the same time, it could be noisy

[@JosecarlosValle]

I am techician of that Friden for 6 years here in Brazil. I am curator of Museu do Computador. I have 1 that . Jose Carlos

[@rickalexander2801]

Love watching these Friden calculator videos. Carl Friden, the man, was my grandfather. I have some of his original drawings that detailed the inner workings of his machine. Never knew him. He died in 1945 and I was born in the late 50's.

[@handyandy6050]

What an amazing mechanical bit of kit!

[@dmk351]

Cave Johnson here.... I punch those numbers into my calculator, it makes a happy face. :D

[@TesserId]

Somehow, I decided that today I would start tracking something down that I'd encountered as a boy. There was a man next door to my Grandmother who repaired these things as well as old adding machines in his gargage. That was in the 60's and 70's (maybe, probably). I was sure that there was a fancy name for these things, but that was before my first hand-held electronic calculator (yeah, an SR-30). So, I may not have know the term calculator when I was first saw these machines. Yet, I don't remember relating the electronic ones back to these. So, I'm at a loss to remember if there might have been a different name for these. The one you have here is closest in appearance to what I saw back then, keeping in mind that I was seeing both motor driven and crank driven models. But, my memory is very fuzzy. Still, I did get to see the gears inside, and I was fascinated that such that the turning of meshed gears could somehow turn into numeric calculations. I suppose it's no surprise that I ended up in Computer Science. You seem to be the one having fun now, and I'm quite jealous. But, I do thank you for sharing that fun.

[@websitesthatneedanem]

Fantastic EFFORT!

[@openskiesmedia]

Thank you for documenting this! It's a wonderful resource for those of us doing more research on the history of the human computers whose lives have become known to us thanks to Hidden Figures.

[@omfgmouse]

Can you explain the square root method in a bit more detail? I didn't really understand what you were doing there.

[@jamesmares4206]

My Dad had one of these on his desk back in the day he would figure out lumber invoices with board footage factors. It was fascinating and impressively noisy.

[@jimh8644]

I used this calculator in the early 70's when I worked in an office with many other users. What a racket! I believe when they became outdated, they were converted to boat anchors.

[@wisteela]

Amazing machine

[@GilmerJohn]

I had a summer job at an observatory. They had several of these machines in the office area. One of the grad students showed me how to calculate square roots by successive subtraction of odd number. (It seems that squares are all the sum of odd number.) In 1961 Friden came up with a machine that automatically did square roots using the same algorithm. It too about a minute or so at maximum accuracy.

[@soundadapter]

I like the old technology Thumbs up many greetings Frank

[@garylangley4502]

My Dad had another model when he was an aerospace engineer. It would do square roots just by pushing one button. If it was a larger number, he said that it would grind away for 5 minutes to get the answer.

[@CuriousMarc]

That’s the Square Root SRQ-10! Quite rare! It’s the last one of these great machines.

[@AngioloHuaman]

wonderful

[@JohnAK72]

Well, that's really nice calculator.

[@TesserId]

I can just imagine something like this showing up in some cold-war sci-fi suspense film. Maybe some student drama project might employ one of these, maybe yours, in a retro film. Gotta wonder if anyone one has written a simulator for this, maybe an smartphone app.

[@alphabetica]

The manual for this is beautiful. It looks so modern in its format. is it online anywhere?

[@CuriousMarc]

I have not seen it. I could find extremely little material about this machine on the web.

[@openskiesmedia]

Scan it? :D

[@CuriousMarc]

I did. Now on my web site at www.curiousmarc.com/mechanical/friden-stw-10-mechnical-calculator Look for the STW user’s manual in the documentation section

[@AhmetcanBA]

I need this

[@olegtarasovrodionov]

You manual is better than that what I found in the web. Can you scan you manual into pdf?

[@violetteclingersmith8792]

Hello, CuriousMarc. I have a 1949 SW 10, very similar to your STW 10. I began dismantling it earlier today, but came across a brown noise-dampening insulation on the inside of the outer casing. As I am not sure what this material is, and am somewhat fearful that it is amosite, I tried to research what it could be but got nowhere. So, I was wondering if you might know what insulation these Friden calculators used.

[@CuriousMarc]

Gasp. I didn't think any of it and did not take any precautions. But I have to say it looked and felt like natural felt to me. But I could have been fooled. In doubt, use a respirator and you should be fine.

[@RyanFriden]

Pretty neat. Thanks for sharing.

[@CuriousMarc]

Are you related to Carl Friden who invented this machine, or is your name pure coincidence?

[@RyanFriden]

CuriousMarc yes, he’s my great grandfather.

[@CuriousMarc]

Sweet! Thanks for posting. He was some mechanical genius! Any family stories about him you can share? Did you get to know him?

[@RyanFriden]

CuriousMarc he unfortunately passed before I was born, so I never knew him personally. But I knew his son Stanley (my grandfather) very well. I have a family biography on Carl in a PDF format that I could email over to you, if you’re interested.

[@CuriousMarc]

@@RyanFriden I sure am. My email contact on my channel about page.

[@daphneblake7889]

I used to have a mechanical calculator. Older than that one...it had a crank on the side you would pull like a slot machine. A row of numbers across the front, and a column of keys for each digit. It would add only(I think) there may have been a subtract function.

[@daphneblake7889]

I think it was called a comptometer

[@fluffymacaw933]

Its like a computer, I wish I had one

[@Radionut]

Oh my gosh I want one of those. But oh my gosh it’s so expensive everywhere you look

[@lowercherty]

People built careers designing, building, and repairing these things for companies like Frieden and Marchant, and suddenly about 1968 it was all obsolete. It, along with very early computers and slide rules, got us to the Moon, though.

[@adenowirus]

I may have missed that in the video, but why does it have two division buttons?

[@CuriousMarc]

You didn't miss anything, I ended up cutting the explanation out when the video got too long. I think this was to get around a patent, some guy had patented the one-button division. But it's actually useful if you do chain calculations. Dividing with two buttons will add the quotient to the previous result, but if you use one button, it will subtract it. So you can calculate things like 3/4+5/8-11/32.

[@user2C47]

Is it possible to mechanically couple the 2 buttons?

[@user2C47]

@@rangarutisersundar8843 I doubt that would work. I would suggest a piece of metal connecting them internally.

[@Not_Lewis]

My grandfather had one of these, but I had no idea what the hell it was at the time.

[@hausaffe100]

can it do exponents? and if yes to what extend only natural number or also real numbers?

[@Darek-qk8zv]

At the moment I'm watching Billy Wilder's The Apartment and I'm interested in the machine that Baxter works in the office. I came across your website and saw this video. Greetings from Poland

[@CuriousMarc]

Watch this one, it explains exactly the sequence they do on film: kzbin.info/www/bejne/Y36vgmOvfpZ1qLM

[@DanBowkley]

I had an old Monroe manual calculator, similar idea to this but with a big hand crank on the side and a little one on the end of the carriage. I think I was seven or eight when it was given to me.

[@TofranBohk]

Nifty!

[@LoneWolfZ]

Seems to operate similar to my Curta in some ways, but quite different in others.

[@puppiesarepower3682]

Math drives the modern world. I wish I had appreciated that fact when I was in school.

[@watchmakerful]

When you are checking the square root, the counter register counts backwards. Why? :-O

[@CuriousMarc]

Алексей Рукин It's because I move the lever to switch it to reverse operation at the beginning of the square root procedure (look at the video at 9:56, and I then demonstrate how the counter works reverse). This way the counter register will represent the square root at the end of the procedure, just before I run the check. This is an advanced feature that was added to the STW-10. It's not present in the earlier ST-10 model.

[@watchmakerful]

CuriousMarc And after that you simply forgot to switch it to the normal position :-D.

[@CuriousMarc]

Алексей Рукин Exactly!

[@emdxemdx]

J’ai commencé ma collection de machines mécaniques avec ce modèle-là… Mais j’ai déjà vu une calculatrice mécanique qui faisait automatiquement les racines carrées. On entrait le nombre sur le clavier comme sur cette Friden, et elle avait une rangée de boutons supplémentaires en bas des zéros. Pour calculer la racine carrée, on appuyait sur le bouton correspondant à la position du point décimal, et après plusieurs minutes de simagrées, le résultat était affiché… (Je ne me souviens pas du modèle, ni comment ça marchait, j’ai vu ça y’a près de 40 ans)…

[@CuriousMarc]

Friden SRQ 10, last of the series. Looks identical to this one. Implements square roots with the method of 5's I demonstrate here, but entirely automatically. Relatively rare.

[@bwhog]

Basically the Monroe system but with more parts and a bit smarter. That ten key is kind of a weird addition, though.

[@guillermofernandezboan2598]

Recently I purchase a Friden STW 10 with a very low serial # 6428. It comes with its electric cord, and once you plug to the AC you can hear it is in mode "on". There is not an "on/off" button on it. This is strange for me: you need to unplug the device in order to get a stop? Or there is another way to obtain this without unplugging it? After some calculations, one of the buttons (the # 4 in the fourth column) gets sticked, and every gentle attempt to release it failed. The worst thing is that the Carriage Clear big button on the right side of the calculator sticks too, causing the calculator enter in an "unceasing operational mood". I need to unplug it just to get a stop! I suppose the reason of this is that my Friden was unused no less than thirty years (could be more). Should I try with a short spray of WD-40? Or you recommend to disassemble the right cover in order to get the Carriage Clear button free? Another question: It is possible to get a pdf version of the User's Manual. It would be very useful to me. Thanks a lot.

[@AureliusR]

Do NOT use WD-40. WD-40 only cleans and displaces water -- it does not lubricate properly! You could use it to clean the joint to get it to free up, but then you need to use proper oil to lubricate. My guess would be 3-in-1 or sewing machine oil would work.

[@RyuuAMcCF]

Most likely your unit was in need of maintenance when you bought it--especially with such a low serial #. My dad used to repair those things back in the '60s when he worked for Friden (and later Sears, which bought out the company), and their insides require exacting tolerances that doesn't allow for much dirt or any worn parts. As a kid, I got to play with the units for a bit after he was done fixing them, and they were a joy to watching them go through their paces! :D It's been over a dozen years since he died and I don't know if he got to keep any of those machines when he was let go by Sears.

[@jedburnell9046]

@@AureliusR If I couldn't fix these with Freon and 3-in-1, it would come to the shop for a chemical bath.

[@Gator141a]

I used one of these in the late 60's at college, while working in the Science Department. The Science department could not afford an electronic calculator (cost $300) but the campus maintenance department had one. Several years I ago I purchased one of these and have been looking for a power cord and operating manual. the power cord socket is like the old two pin that powered TV sets, but with a third prong. I would appreciate any help in locating these items (a pdf would be fine) thanks in advance

[@CuriousMarc]

+Gator141a The power cords are easy to get. Look for Oval Power Cords or IEC power cords on ebay. Or buy directly from here: www.apexjr.com/wire.html#Power

[@Gator141a]

These are much older then IEC (rectangular slots) In prehistoric times (vacuum tube) tv's had 2 small round pins on their chassis, about a half inch apart. This calculator has the "new" improved type with a third (ground pin)

[@Am0re98]

try to divide by zero

[@ffggddss]

He (CuriousMarc) has another video where he does that very thing. It was posted 2016 Jun 13 : kzbin.info/www/bejne/bXzHZIWVh9GLncU Fred

[@fridenyg8222]

good

[@kiningroseburg9288]

I want one!

[@volodyanarchist]

1

[@leroyvargas9500]

Where can I buy that monster machine? And how much does it cost?

[@olegtarasovrodionov]

You did 12.24744871 times 12.24744870 instead of 12.24744870 squared

[@CuriousMarc]

+Олег Тарасов Yes I know... Thanks for watching closely...

[@DiegoPerez-wj1oq]

Tengo una igual,No tengo manual. Como se pondría conseguir? Abrazo desde uruguay

[@christiaandockers3755]

I own one. restoring it right now

[@CuriousMarc]

Good luck! The service manuals are now available on my website www.curiousmarc.com/mechanical/friden-stw-10-mechnical-calculator

[@christiaandockers3755]

@@CuriousMarc Wow! Thank you so much!

[@wcodelyoko]

Try (100/3)*3

[@iamjimfan]

We should appreciate the computing power we have nowadays

[@Karinmatica]

I have one of these machines, older I think, but I have not the power cable, so do not know if it works... I want to sale it! Do you know how or where can I do it? Thank you

[@CuriousMarc]

+karin bertolino ebay... That's where mine came from...

[@Karinmatica]

Ahhh ok, thank you a lot!

[@The4stro]

imagine bringing this to a math test

[@roachtoasties]

Performs better than Windows 10.

[@marinadesouza1658]

True

[@igotbored8931]

Where do I get

[@roachtoasties]

Cool. I'm dumping Windows machine for a Friden STW10.

[@jaimdiojtar]

does this machine had any computer in it or software written for it? how could this machine divide infinitely by zero or do math in general?

[@themanofiron785]

It's just doing what you were taught in school, but it's using rotating gears to actually do it.

[@alanfreeman1838]

I USED TO TEACH TECHNICIANS HOW TO REPAIR AND SERVICE THESE MACHINES IN ROCHESTER N.Y. AND IN SAN LEANDRO CAL

[@tomcarver6969]

was one of the reps that trained in NY. good to hear the friden shuffle.

[@Bobloblaw624]

How do people create something like this?!

[@kayswithin2787]

How can I get one?

[@gamingparlour1732]

this is how the they did the calculations to design a nuclear bomb...insane

[@lowercherty]

This and slide rules. Back then Computers were people sitting in a room working these things doing calculations per a written script. Watch the movie Hidden Figures.

[@bareq1981]

Judging by the condition of the handbook, I can see that not much has changed for the last 60 years, noone read manuals back then either

[@rayhorner2965]

If you do the calculation on the survey, it takes hours to calculate.

[@oida10000]

Why does it have any key like 10 times?

[@garydunken7934]

What's the weight of this mechanical calculator?

[@lowercherty]

As I remember 20 to 30 pounds.

[@michelesestu]

Please make a division by zero

[@CuriousMarc]

Michele Sestu Deus That would be an interesting experiment... I think it jams several machines of that vintage. So, why don't you do it on your own machine first :-)

[@michelesestu]

CuriousMarc I can try it on my piano only :/

[@CuriousMarc]

Michele Sestu Deus Yes, saw that, nice piano playing! I play too.

[@watchmakerful]

Michele Sestu Deus Division by zero on such machines cause them to rotate continuously.

[@csean97]

Алексей Рукин Yes, division by zero causes the machine to run continuously ... but that is why there is the "DIV / STOP" key ... raise the key up, and that will stop the machine; after which one can press "CARR / CLEAR" or do some other operation. The key can also be moved down to stop a division in the middle of the divide operation.

[@wardrich]

This is cool as shit! I want one lol

[@mysock351C]

I think the slide rule beats it on square roots.

[@ffggddss]

Well, in speed, sure; but certainly not in number of significant digits! Fred

[@miles2378]

What is the point of having all those rows of number keys?

[@VisibleReality]

It's one digit per column, so to input a number the ones digit goes on the rightmost column, the tens digit in the second rightmost, and so on.

[@rareform6747]

Comptometer , take that into the school room without being caught ?

[@groszak1]

why is this calculator called "Hidden Figures"?

[@CuriousMarc]

The Friden STW10 is the calculator machine that sits prominently on the desk of Katherine Johnson in the movie Hidden Figures.

[@iosef3337]

Why not make transistors with mirrors and instead of electricity, use light?

[@MelvinGundlach]

iosef 333 Because you cannot catch light as easily as you can catch electricity. Also electricity has much more energy to work with.

[@piotralanp]

Try building a prototype nobel awaits if you're right ;)

[@thorstendinkelmeier8274]

Calculate 2+2 - 3 because its quickmaths

[@wll1500]

Smoke trees

[@George040270]

Why does it need so many numbered buttons?

[@CaptainWumbo]

George Pierson Each column of numbers is attached to one gear. Mechanical calculators work by setting the number of teeth in a gear that will tick up the accumulator. So the number you press sets the number of teeth for that place in the number (tens, hundreds, thousands etc).

[@inandio]

The funny thing is that I can compute not only addition, subtraction, multiplication and division but also trigonometry, roots, logarithms (natural, decimal or deliberate), percentage and ratios with only a slide rule and an abacus.

[@user-xf7nn9zt4z]

Would you be interested in selling this ?

[@petersmit7650]

so glad i was minus 10 years old at the time...

[@raizon5530]

Wow, I

[@snshusat161]

To use calculators would have been called a skill back then

[@theshiberealm9022]

imagine this is giant thing is the only piece that aliens find of the human-race

[@KameraShy]

Brought back memories. Had to use one in my accounting job in 1974. Really cheap company. Late 60's the statistics class lab was full of these things, dozens of them. The racket of 30 machines running at the same time was deafening. Probably caused Boomer hearing loss.

[@dfpytwa]

Cool now send it to Taofledermaus so we can watch him test slugs on it.

[@nathanpratt3058]

Who knew u had to know how to do math before u could even use a calculator to do math u dont know

[@yowut8075]

WE

[@gabeh9748]

Ban fully automatic calculators