Kyle Rankin @kyle@librem.one

Like with other Comptometers, you just press corresponding keys to add. Trained Comptometer operators performed calculations by feel (odd keys were concave, even were flat) and mostly one-handed so their eyes and left hand could stay on the sheet of figures. Here's 31337 + 5.

The Comptometer to the right is a Model F, made between 1919 and 1920. It is the mass-produced successor to the smaller (and rarer) Model E (1913-1914) to the left. The Model E introduced a "control-key" mechanism to prevent errors from half-presses, but Model F simplified it.

@elb It's a National Cash Register Model 11-EN made in the early 1950s. NCR was better known for their ornate cash registers, but they also made electromechanical adding machines like this one. They apparently were also involved in manufacturing electromechanical Bombe computers during WWII to crack Enigma.

I'm not add-icted. I can subtract whenever I want. Of course to subtract I would need to add something complementary...

The server's anti-virus wasn't up to date... https://arstechnica.com/information-technology/2021/10/passengers-couldnt-fly-after-nhs-vaccine-passport-went-offline/

@jlcrawf There's more to come! I'm going to feature a new one weekly, spaced out so as not to deluge my timeline all at once.

@ajmartinez There is also this, but the original site is offline now so we'd have to rely on wayback machine: https://www.thingiverse.com/thing:1813308

@ajmartinez That would be an incredibly fun project. Most of the replica kits I see out there just replicate the outside, the inside is an arduino or similar. I'd love to replicate a mechanical version.

Apparently there are CAD renders here: https://grabcad.com/library/enigma-machine-replica-1#!

Eventually John Conner will drop from the future into that street. That much is known, the machines just don't know exactly when. https://sanfrancisco.cbslocal.com/2021/10/14/dead-end-sf-street-plagued-with-confused-waymo-cars-trying-to-turn-around-every-5-minutes/

We are testing out a new experimental feature in PureBoot to extend tamper detection past /boot into the root disk. I write about the feature and my thought process behind developing it here: https://puri.sm/posts/new-pureboot-feature-scanning-root-for-tampering/

"I'm really into mechanical calculators and also security. A mechanical cipher machine would be really cool to add to the collection." Then I saw the going rates for vintage WWII cipher machines... #nope #toorichformyblood

@yaelwrites Especially this time of year!

The Burroughs adding machines aren't my favorite to use, but they are my favorite to look at. Check out the lines on this 100-year-old Class 3. It reminds me of sedans from that era.

There are few things as satisfying as fixing something you are unfamiliar with by researching how it works and applying basic troubleshooting skills. In other news, the furnace works again (insufficent pilot light flame around the thermocouple).

Adding to my collection...

Due to the size and the case design, I suspect Addometers were mostly stored on or in desks and pulled out for quick arithmetic and they work well for that. The Imperial model I have was probably thrown in a toolbox and has lots of wear and even initials carved in it.

As I mentioned the Model C was designed for Imperial measurements and had a dial that went up to 11 so inches could carry over into feet. Here I'm calculating 2' 9 3/4" + 1' 6 7/8". Doing math with Imperial measurements really makes you appreciate the Metric system.

You can also perform division using the repeated subtraction method but you have to keep track of the number of subtractions in your head. To clear the registers, just pull on the lever on the right side. This also ejects the stylus for you if it's in storage.

To multiply, perform repeated addition and shift left for each term in the multiplier. Here is 12 x 12.