How do I operate this vintage calculator?
December 28, 2010 7:38 PM   Subscribe

Help me learn to operate this Monroe High Speed Adding Calculator.

This relic came into my possession when my grandmother moved from her house into a senior apartment. She used it weekly for half a century, but sadly can no longer remember how it works. I've been able to add and subtract, and I know it's capable of at least multiplication and division, but I can't figure out how it's done. There's a lever on the top left with a division sign on it, and throwing it causes a knob on the right side of the machine to spin. This site has info on the history of the Monroe company, and offers printed reproductions of manuals for other models, but I'd rather not have to order anything.
posted by TrialByMedia to Technology (3 answers total)
What a neat machine! It looks like a (partial?) clone of the Friden calculating machine; maybe you can find more information on that one since it was very popular. There is a nice description here and holy crap look at those innards.
posted by fritley at 9:00 PM on December 28, 2010

Those things are awesome- they had something like that at my bank when I was a kid, on the "courtesy" counter where you filled out your deposit tickets.

The basics are this: it is an adding machine, so it works slightly backwards from "normal" calculators. You enter a number, and then you tell the machine what to do with that number. As the linked thing says, your running total is stored in an accumulator.

So 2 + 2 gets entered as

2 +
2 +

You decide where the decimal is for that session. If you need two decimal places, the right two columns are the right two digits of your number. Even if they are zero, you have to "enter" 0.

So, if you are adding

472.12 +
553.98 +

You hit the 2 in the right column, then the 1 in the next one, and move left. Once it is entered, hit plus. (Or crank the crank- going to take some figuring out).

Once you do that, the buttons are reset and you can enter the next number, working right to left. Then you hit the total key and you get your answer.

That's all I know.
posted by gjc at 5:25 AM on December 29, 2010

That calculator looks very cool. I'm jealous.
posted by wittgenstein at 6:16 PM on December 31, 2010

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