Precisa 102-1 adding machine

The Precisa 102-1 adding machine was made in Switzerland in the early 1950s. It has some quirks that you need to be aware of when using it, and its recall functionality is very unusual.
For more information on this machine and others in my collection, please visit my website:
www.jaapsch.net/mechcalc/
0:00 Introduction
0:51 Addition
1:16 Totals and subtotals
1:58 Subtraction
2:25 Negative totals
3:30 Non-add
3:55 Non-print
4:29 Repeat, multiplication
5:34 Recall
8:17 Crossbow logo
8:50 Opening the case
10:25 Printing mechanism
11:01 Subtraction mechanism
11:53 Non-print mechanism
12:40 Reassembling case
13:08 Outro

[@stephenfreeborn]

Love how that paper roller mechanism comes off.

[@brunopacifico4979]

Thanks for sharing!

[@GrumpyTim]

Unusual user interface, with the + - lever and negative results, but you'd get used to that pretty quickly. The recall button is excellent, I wonder what method it uses to be able to do that, that's pretty impressive. Definitely a great little machine Jaap.

[@jaapsch2]

The recall button even recalls a number printed with the Non-Add button! I wasn't able to find a manual, so when I was servicing it, it took me quite a while to realise the (sub)total buttons weren't stuck.

[@GrumpyTim]

@@jaapsch2 Yeah, it was a bit of a surprise that it locks them until you pull the handle for the line space - always interesting to see the little quirks that different manufacturers come up with.

[@guldilo]

The lock of the total und subtotal buttons probably has this reason: When you add two numbers, first the addition is done without carry (this wouldn't be possible) and only at some time later the carry is processed. This machine does the carry for the last addition only at the beginning of the next addition. It isn't able to do it before recalling the result. That's why you have to add a 0 to get a correct result.

[@jaapsch2]

I haven't examined the inner workings very closely. I thought it might have something to do with the recall mechanism, but your explanation sounds very plausible. Edit: I've looked at how the register wheels move and it turns out this is not the case for this machine. The digits are added during the first part of the return motion of the lever, and the carries are performed during the final part of the return. I can't really see much happening during the blank stroke.

[@zse8861]

On the Remington-Rand adding machine you have to go through the same procedure: pull the handle without any input to unlock the total buttons. Is there a way on this machine to release the subtotal and total buttons if you depressed accidentally?

[@jaapsch2]

Yes, the input clearing button also releases any of the function buttons that were pressed except for the Non-Print button. It even releases the Repeat/Multiply button despite the fact that this button can be released just like the Non-Print button.

[@sonoio2002]

Did I miss what the numerical display is used for?

[@jaapsch2]

It's not a numerical display. The zeroes are just painted on the window behind which is the pointer that indicates how many digits have been entered so far.

[@sonoio2002]

@@jaapsch2 that`s a little bit weird even for swiss standards ...

[@MattMcIrvin]

@@sonoio2002 It was pretty common for these printing ten-key adding machines to have no display, just a little window with a pointer showing how many digits you'd entered. But usually it just said "12345678" or something like that.