The Star Adding Machine

This is the Star Adding Machine. It was made by the Todd Protectograph Company. It says so on the label on the front right here. It was made in about 1922 or 23. The first version of this machine was made by the Accounting Machine Corporation, and they made it between 1918 and 1922 after which they sold the rights to make and sell it to the Todd Protectograph Company. It has a seven digit register, and in front of each digit in the register is this kind of paddle wheel that you use to input the numbers. It’s very simple. You just put your finger next to the digit you want to enter and pull down, and release the wheel and it springs back. That adds that digit to the register.

01:11 - If you enter another number it adds it, and it will carry automatically. The carry is done using a spring-loaded mechanism, a stored energy mechanism, so there’s no extra effort required when you enter the number and it carries. To clear the number you use this small lever. Those same springs that do the carry also reset the numbers. In about 1923 they made slight changes to this machine.

01:59 - They added a carrying handle, and that handle could also fold down over the input board, and it would lock these paddle wheels in place, as well as this clearing lever, so that it would keep whatever was in the register safe. That handle could then be released using one of these buttons. A year later, in 1924, they changed that to a whole cover that could fold down and lock with a key to make it even safer. And two years after that, in 1926 they changed the machine to have an input register so they had a register that showed what number you’d entered. That version was called the Todd Visible Adding Machine and they stopped making that in 1928.

03:05 - So versions of this machine were in production from 1918 till 1928. As you can see there’s also these small digits here. Those are the complementary digits and they allow you to do subtraction So if i wanted to subtract, say, 28 I would enter the 8 using the small digit here, and a two using this small digit and I’d also have to enter all the leading zeros. and the result is then correct, 48. All those leading zeros, that’s a bit of a pain to enter, so they also added these buttons at the top. Each button prevents a carry from occurring, from the lower digit to the digit that the button is above.

04:16 - So if I hold down this button, it will prevent a carry from happening to that digit. So if i hold down this button, this zero should not change if i enter something here. And that allows you to shortcut entering all those leading zeros when you do subtraction. You might have noticed these small buttons at the front. That’s a braking mechanism. So when your finger hits the bottom here it pushes down that button, and that ensures that the register number wheel will not overshoot.

05:07 - However fast you pull down, it immediately stops moving as soon as you hit this bottom button. So that was the Star Adding Machine by the Todd Protectograph Company. Thank you for watching! .