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Good morning! Welcome back to the ValorosoIT channel, the channel dedicated to vintage computers and electronics. But today we are not talking about computers or electronics, but rather about this Facit CM 2-16 mechanical calculator. In fact, this video is included in the column The latest discovery in retrotechnology, so we are not just talking about computers on this channel, but in any case about vintage objects.
I had already shown you this calculator in some short video. In a first short video we had done the unboxing, so when I purchased it. In a second short video I tried to do a couple of sums, just to see if the calculator worked. And it worked, luckily! In a third short video I showed you the inside of this mechanical calculator, so much so that I disassembled it, then I also cleaned it and now it is in excellent condition.
Why did I get this passion for vintage calculators? Well, I went to visit a Historybit exhibition and, at that point, seeing all these mechanical calculators, I couldn't help but fall in love. So, now I've bought myself one... actually, more than one! If you have also seen the other short videos, I also bought some electromechanical calculators. One didn't work, I'm trying to fix it little by little. Inside, the mechanisms are quite complex and, therefore, maybe once you manage to make one operation work, but then another doesn't work. In short, that's how it works.
I got tired of just adding and subtracting with this mechanical calculator, so I downloaded the calculator manual online. You can also find it on my website www.valoroso.it, if you click the link in the description: I have created a page relating to this video with also the calculator manual, in English, to download. Now let's try to carry out all the operations that this calculator is capable of doing: therefore additions, subtractions, where to put the decimal point, multiplications and even divisions.
Let's take a first look at the commands and components of this calculator. First of all we can notice three displays: 1, 2 and 3, which are called registers in English. In fact, the manual that you can then download is in English, so you can find them as register. The first register is this one for insertion, this one down here. In fact, if I type a number on the keyboard, for example 1, 2, 3, 4, 5, 6, this number is displayed in the entry register. In English, this number is called the setting register.
By moving this crank, called crank in English, the number present on the insertion register is transferred to the accumulator, which is this other register up here, this other display. If I move the crank clockwise, the number is added; if I move it counterclockwise, therefore backwards, the number is subtracted. So now let's bring it back up. This one, however, on the right is the counter register, otherwise called multiplier register, and is used to count how many times I have entered this number from the settings register to the accumulator. It is useful in multiplications. The accumulator, in English, is called product register, so you can find it in the manual.
As for the buttons, we have these two shift keys. The first is used to move one position to the left and this white dot also moves, where there are all these other black dots, which indicates the decimal point. In fact, we have moved one position to the left, it is as if it were a ten and, therefore, we find the comma in this second position, thus in the third. With this other one, however, we can go back.
We also find these two buttons, which are called tab keys. They are used to move the insertion register carriage to the left, in this case here, with the rightmost button up to position 11. Instead, with this button here, everything is completely at the bottom. Let's reset and try the two tabulations: 1, 2, 3, it moves up to position 11. Let's reset: 1, 2, 3. With this one it moves completely to the bottom and, as you can see, the decimal point dot also moves.
Let's also look at what all these levers are on the side. As we saw before, this here is the crank for doing additions, turning it clockwise, and subtractions, turning it anti-clockwise. This lever here on the right is the reset lever of the insertion register, so any number that I type, when I push this lever up, is reset and the carriage is moved all the way to the right. The proof that it is zeroed is that if I now move it to the left using the tab key, I will see that everything is zero.
Instead, these two levers on the left, these two here, are the two reset levers of the accumulator, therefore of the product register, and of the counter, therefore of the multiplier register. For example, if I type 5, 5, 5 and continue to add three times, as if we had done it three times, to reset the accumulator I press this lever down and now it is at zero. To reset the counter, I push this lever down and it goes to zero.
If I bring this number, 555, from the insertion register to the accumulator, therefore as if I added it or multiplied it by one, I also have another possibility, given by this lever. This lever is called back transfer, and is used to transfer the number found in the accumulator to the insertion register.
Now let's reset the insertion register to test it. We must put a certain number of zeros at least equal to the number of positions we want to bring from the accumulation to the insertion register. For example, I can add four and then, through this lever, I can bring the number down here. In fact I see: 555.
This operation is useful, for example, if I want to add three numbers. I will find it here on the accumulator and, after that, I will be able to multiply it by another number. I need this number above here below to then multiply it.
Well, this is getting pretty complicated! Let's look at the manual. We have some early examples in the manual. For example, it explains how to make a sum. I would do exactly what the manual tells us, so we can learn and you can follow it too if you go and download the manual online, on my website.
Now let's reset everything. The manual suggests making a first sum of 3478. We are talking about whole numbers, so these here, which are the decimal point indicators, are not of interest to us at the moment.
First sum: 3478. Ok, (sum) plus. We rotate the crank clockwise.
394. Ah no, before entering the number I have to reset the entry register.
394, sum.
85, sum.
8962, sum.
It gives me a total of 4 numbers entered and the sum of 12919.
If you want, you can also try it with a slightly more modern calculator that is not mechanical.
Ok, we've done the first sum. Now we can test a subtraction.
Let's reset. Let's also reset the upper registers and do this subtraction. We have two types of subtractions, I see. A subtraction where the result is a positive number and a subtraction where the result is a negative number.
Let's go over the first example, then a subtraction where the result will be a positive number:
276543. But can you hear how beautiful the noises of this calculator are? Now that's ASMR!
We need to turn the lever clockwise because we need to load this number into the accumulator.
We reset the entry register and type 80927.
However, at this point, to subtract this number from the one already present on the accumulator, I will rotate the crank anticlockwise.
So we have a result which is 195616. Let's see if that's right. Yes, even the manual says it's right.
If you want, try it too and then let me know, because if both the calculator and the manual are wrong, then we can say that the manufacturer wanted to play a trick on us!
Now let's try subzero subtraction. We zero everything with all the zeroing levers. He offers us this operation:
58923. Now I'll keep quiet, so you can hear the numbers as I type them.
93470, to be subtracted.
Did you hear the bell ring? It's because we went below zero. So we have all 9 and then a number here.
At this point he suggests we add another 8463. Ah, we always need to reset the insertion register.
So let's go clockwise. Perfect.
We find a number that has very little to do with an understandable number, because it is: 9999…73916.
So, what does the manual offer us? You too, if you want, can read it to try this operation here.
Maybe I followed a slightly different procedure than the one indicated in the manual. Now we need to bring this number down here.
So we reset the insertion register, we put a certain number of zeros in it, higher than what we see, therefore higher than 73916, and we move, then transfer with the back transfer mechanism, the number from the accumulator to the insertion register.
Okay, here it is. And then we need to make a counterclockwise turn of the crank.
Oh, here it is! 26084, with a negative sign, because this red dot lit up. However, when it's turned on it's nothing electrical, so there's simply something red behind it that can be seen.
Let's see if it's true that it should give me -26084? Yes, the result is -26084. We must obviously neglect all the other nine that we see above.
It's really simple, eh, this calculator! Really simple to use.
Well, let's clear everything up a bit. Here you go.
Now… multiplication. I'm already dying! Whole numbers, at least this one!
The manual offers us: 6943259 * 2043. Now, I would have several possibilities to do this operation. The first would be to rotate this handle 2043 times, until we reach 2043 here, and at that point we would have the result here. But no, it's not worth it... So I can go back and do what the manual suggests. We need to write 2043 here on the counter register.
Let's start with the first three, so: 3. Then we have to put 4 on this second digit here. We move with the shift key to the left by one position. At this point I rotate the crank four times, always clockwise because I am continuing to add. Here we are at 0, and here 2. So we have 2043.
The result is enormous, and how can we see it here? We have the first three and the second three… are they billions? 14 billion, 185 million, 78 thousand, 137. Ok, that's right. According to the manual, that's right. Simple, huh? Simple, this multiplication is already starting to give you a bit of a headache!
Let's move forward in the manual a little, because otherwise, if we have to scroll through it all, we won't be able to do it anymore. Let's add numbers and then multiply them. Initially we do the sum. We are on page 8 of the manual, if you want to follow me.
367 +
9124 +
461 +
81
Note that I could also have done some subtractions, because all I had to do was turn the crank backwards and I would have subtracted that number there. Well, it gives me 10033 as the sum of the previously entered numbers.
At this point we need to multiply them. We create space, so we need five digits to transfer the number. We transfer it with the back transfer lever, so the number from up here goes from the accumulator to the insertion register. At this point we multiply it by 113.
Let's start with the first three: 1, 2, 3. We move one…
Here you go! On the accumulator register we have the multiplication of the previously made sum and 113. Does this give us... what value? 1133729, which is right, as the manual also says.
Oh, by the way, since we talk about all these boring topics on this channel, if you haven't signed up so far, keep not signing up, because... that's always the situation. It's always like this! Either there is a repair that gives you a headache, or there is a product that is difficult to configure, or we are talking about who knows what. Anyway, still old stuff. So consider carefully whether to sign up or not.
Division! Division…
The division is complicated, it took me a while to understand it, eh! So… best wishes, best wishes! The first division proposed to us in the manual is 9955128 / 302.
Let's move everything to the left with the tab key and it ends here. Let's go around clockwise, reset everything, but not this one at the top, not the accumulator. At this point we have to do: divided by 302. We type 302 and always move this 302 to the left.
This is where the situation gets complicated. You need to turn this crank counterclockwise until the bell rings. Let's try... Ok, let's go around forward again.
When the bell rings it means that we have gone further, therefore below zero. We need to take a turn forward again. We found the first number of the division result, here: 3.
Now, using the shift key on the right, we move the insertion register carriage one position to the right and continue by rotating the crank anticlockwise. Ok, I heard the beep. I did one more lap, then went back until I was back in the positive numbers.
And with that said, let's move on. Let's move to the right one more position in the insertion register, rotate counterclockwise. Ok, let's go back and we're at 329. We've done the first three digits of the division result.
Same thing: we move to the right to another position. Then, if you proceed too far and perhaps the lever gets stuck, you have to continue counterclockwise and then return clockwise until it dings a second time.
Ok, up here we are at zero. So it means that, in the accumulator register, we have removed everything we could remove. The result of our division is 32964, also indicated with the white dot above, on the last whole digit. So we have 32964. Let's see if it's true: 9955128 / 302 = 32964. Perfect!
I mean, but you need a degree to use this calculator! Let's go back to the manual, because the story doesn't end here. We also need to go and study how the decimal point settings work.
Let's reset everything. Well, it's very easy about subtractions and additions. If I set, as if they were euros, with two decimal places, I move... this to the second decimal place, ok? Now let's do: 5.50 + 6.50. And we have 12.00. I can also add 0.25 (so 25 cents) and we go to 12.25.
Now, if I want to make 12.25 × 3, I bring the whole number here and, at this point, I add it three times: 1, 2 and 3. Result: 36.75. So for addition and subtraction, rather than simple multiplication, it's easy. Subtraction is equally simple: do we want to subtract 10? We make a turn counterclockwise and from 36.75 we arrive at 26.75. When it comes to additions, subtractions, and multiplications of integers, decimal handling is quite simple.
As for multiplication, however, it is a little more complicated, because the decimals are added. For example, we want to do the multiplication 3.18 × 5.123, which is what we find on page 13 of the manual. Here there are two decimal places that we need to put for the 3.18 (insert register), and 3 decimal places that we need to have on the counter register. In the accumulator, however, we must reach 5 decimal places. Will it work? We see.
I enter 3.18. Okay. Here we have to go and put 5.123. Let's start with the 3...
Ok, oh well, the 3.18 has transformed in the meantime, but that was it. 3.18 × 5.123 is 16.29114. Right! We did it! Damn, but really, you need to have the manual to do these multiplications. Otherwise, it's a mess.
Are we ready? Are we ready to make this division? So, 525.16 ÷ 3.5.
We bring everything to the left, above, as we did before for the other division. Now, I'm not going to show you all the steps because I'm doing them in my head. I already have a hard time doing them, and in any case we've already seen them before. At most, go back in the video and watch them again.
So, we entered 525.16. We reset the counter register and put 3.5. Okay. Here, we have 13 decimal places in the accumulator (product register), as indicated by the number 13.
Instead, below here we have 15, which however we must consider, because we must see the internal number, which is 7. I bring the camera here so that it can be seen. Inside, here, there is a second number, 7. The manual says to look at that. So: 13 - 7 = 6. We need to set the decimal point of the counter register to 6.
At this point, the result will have three whole positions; everything else will be decimals. We continue with the subtractions until we hear the bell ring. Then we move the cart forward, to the right, with the shift key and continue.
We did it! Then, the result is exactly the same as what the manual says. However, if we want to look with the calculator: 525.16 / 3.5 = 150.045714... and other little things.
Oh, we even managed to divide with a comma! It was difficult, but we did it.
But how did they do the math in the 1960s? So, this calculator was produced from 1959 to 1967, so maybe towards the end of the 50s we were having a little more difficulty. Then, perhaps someone who was in the office doing calculations was already a cultured person, so there are all these difficulties in using this calculator.
But, really, it was very complicated. It was very complicated! It's definitely something that needed to be learned. Because it's nice to know how things were done once upon a time, and so I'm glad I did.
I hope I haven't bored you too much. In fact, the video was quite static on the operations of the calculator, but this is what we had to do. If you like these topics, especially vintage computers and electronics, I invite you to subscribe to the @ValorosoIT channel and activate the notification bell.
And we'll see you in the next video! See you soon! Bye bye!