The Comptometer Super Totalizer, a mechanical calculator.

This is a mechanical calculator, the Comptometer by Felt & Tarrant. This is a special version of the Model J, called the Super Totalizer.
I explain how it works, and what all the buttons and levers do.
This one has serial numbers J317903 and S1415. From the range of serial numbers found, it seems that some 85900 model J Comptometers were made, of which maybe 2000 were Super Totalizers.
This one has had a little restoration work done. Nine of the keys have had new tops fitted at some point. The windows over the digits seems to have been changed from celluloid film to more modern transparent plastic. Other than that it seems all original.
Some minor corrections and additions:
I say in the video that it was made in 1931, but it is more likely to be 1934 or 1935, as the patents were filed in November 1934.
The black paint on the case decoration is probably original. It looks like models H and J had this painted black, but earlier versions like the model F did not.
The blinds on the digits of the front register do a bit more than just cover up a digit. It also blocks any carries from that digit, so any hidden wheels cannot affect the visible ones.
You can find more information on my site:
www.jaapsch.net/mechcalc/
For a more detailed explanation of performing arithmetic on the Comptometer, see my other video:
• Comptometer Arithmetic

[@randywatson8347]

If the world is in total chaos, this calculator will still operate :-)

[@JAYGMART]

Enjoyed this as I used to use these machines at work. Thanks

[@judithfaber2667]

Me too! I feel very old

[@richfiles]

Makes my 8 digit basic comptometer feel almost inadequate! :P Very, VERY cool machine!

[@jaapsch2]

richfiles Thanks! If you want to see some photos and read a bit more about this machine, follow the link at the bottom of the video description.

[@daphneblake7889]

I used to have one of these, (without the super totalizer on the front...it was one of the older ones with the larger crank that had to be push-pulled. Its been several years since ive had it but i believe it had 12 columns i never knew how to use it. All i can remember is how dam HEAVY the thing was!

[@ptonpc]

That is beautiful :)

[@bwhog]

Excellent video. I SO want one of these! Interesting note about the zeroing. I didn't realize that. I'm rather surprised that there was not a "bell on/of" lever introduced on these since I can imagine ten of these in a room must have been just annoying as heck. I'm trying to learn how to use these, not because I have need of it, but understanding how the operators used them is part of the historical interest. I haven't quite figured out how to cope with the error detection yet. Most of the time, it just seems to get in the way. I suppose that's because there are no experienced operators available to me to say, "Hey, dummy, do this!" Remember, qualified operators were expected to be able to clear the machine, add a column of 10 two digit numbers, and write the correct total down in about 16 seconds. You didn't do the subtraction quite right. You're subtracting one digit. Therefore, it is only necessary to hold the "carry cutoff" before the next highest digit and simply subtract 1 (add 9) in that first column. So subtract 12 from 1234. Hold the cutoff to the left of the 3, and then, using the small numbers, subtract one less (11, or add 88). Boom. 1222 is displayed. It gets more interesting when you want to subtract 3 from 10001. Then you have to "borrow" to do the job. However, you can't just borrow from the first digit as you would in other cases because repeated zeros cause problems for this method of subtraction (addition by adding the 9s complement of the number.) So you have to borrow all the way over manually and then subtract 2 (one less than three) and hold the cutoff when you do. You WILL get the right answer but sometimes its easier to do subtraction in your head or on paper than on the machine. The "less one" also applies to sequential multiplication (third factor and beyond) and division.

[@jaapsch2]

I tried to keep the explanation simple, just enough to explain what the carry suppression buttons are for. I made another video where I explain arithmetic in much more detail.

[@bwhog]

@@jaapsch2 👍

[@brunopacifico4979]

Fantastic!

[@daphneblake7889]

I own one of these, (12 column without the totalizer) and it also has the black detailing.

[@daphneblake7889]

How do you subtract 99 from a number say 555-99=456? Must enter a +901 Co digets 0_1 There is no co diget "9" Is it normal to not press anything when subtracting a 9 like when adding a zero?

[@jaapsch2]

Yes. The complement of 99 is 01, possibly with leading nines. To subtract 99, you actually add (9)01 and therefore don't have to press any button in the second column.

[@Omnihil777]

Thanks, never actually seen a Super Totalizer model. I wonder what I would've to pay for one IF i find one... Just wondering. I absolutely LOVE these machines, alone the feel of the numbers, the look of the plastics/bakelite - awesome! Stole the sound from the long over-carry for my phone. No really, i did. Thx! Edit: Here is the link to the sound as mp3 from 6:33 : my.pcloud.com/publink/show?code=XZg81wZroEXgvjJPtjTAyoNdfk1GmYUXgpV

[@jaapsch2]

The one you see in this video cost me 130 Euro, and needed no work done on it at all. The STs are very rare in the USA, not so much in the Benelux. There may have been a factory (or an assembly plant) here in the Netherlands that produced them.

[@Omnihil777]

Jaap Scherphuis you made quite a bargain there, cool. I've seen standard models in good condition for 300 and more.

[@LoyalToEden]

I actually have one, in perfect working condition, build in 1932. But it is not for sale. According to sources on the net there are very few still around, working ones even less. Hope you find one ...

[@BiLatKnee]

"150,000 GIRLS"! I came here because I saw an ad in a 1957 newspaper from Jackson, MI headlined, "150,000 GIRLS". Ad goes on to say, "Yes this is the number of Comptometer Operators need yearly by industry throughout the country. Prestige, excellent salary and job security are but a few of the advantages of being a Comptometer Operator. Prepare yourself for an excellent office position by enrolling in your Jackson Comptometer School. Short, low tuition courses. Day or evening classes. Free Placement service. Dial ST#-#### for free trial lesson." Good to see that men (and presumably, women) can actually operate these machines as well! =8-)

[@ag6371]

It's also called model ST.

[@johneygd]

I still don’t understand it haha.