In 1963 if you wanted to do calculations You had a mechanical calculator like thiswonderful odd nur brunsviga, but it’s all mechanical this guy 1962-63 Bob Dragan worked at Frieden incorporated maker of mechanical calculators had this idea let’s invent an all-electronic calculator indeed Nothing mechanical in it.
It’s all electronic, and I’ve been lucky enough to Not just get one of them But to meet and talk with the late Bob Reagan who came by and helped me repair two of them signed by Bob Reagan August 2006 this is a cathode ray tube out of an oscilloscope four circuit boards It’s all discrete transistors each one of these is one transistor each of these probably cost five or ten dollars in 1962 germanium transistors Resistors diodes circuit boards that are not just double sided but sort of in an odd way four sided it Folds in on itself plugs in and there are four different But even that’s not what I find amazing in a Calculator you have to keep track. You need a memory you need to keep track of the numbers Where’s the memory this used a piece of piano wire for memory You would tweak one end of the piano wire vibrate Go around around around in a spiral and at the far end there’d be a little microphone to hear it each pulse Was a ding Ding it was called recirculating audio acoustic memory.
It’s all in here the number 5 Binary zero one zero one had to have ding no ding ding So a ding was a bit it remembers in time it takes about Oh A hundredth of a second for these little bits to go around this long spiral come on over Freddie check this out Now let’s look over here First you can see there’s a spiral out here every time.
There’s a bit like the first the first bit in the number five over here is a little speaker that goes point little magnetic coil it so it goes point and launches a Pulse a little blink goes around here on the spiral of piano wire steel wire It spirals in then spirals out and a couple of milliseconds later it gets to the far End where there’s a tiny microphone and amplify microphone over here Which goes out into an amplifier and then into the circuit boards? So the memory of this calculator is all acoustic Ever there every time you type a number into it the bitstream of the number is represented continuously as Vibrations in this wire the alternative of course is what we do today. You’d have solid-state memory Well solid-state memory well there’s Five let’s say there’s six Entries in the stack each one has say ten digits.
It’s more than that’s 13 digits well Let’s say ten times six is sixty digits times four bits per digit It’s on the order of 250. Maybe if I I would need somewhere between 200 and 500 transistors and each transistor is costing me a dollar that’s big bucks and On top of that it takes up space so rather than using Transistors as we would today for memory put all the information in Acoustic memory okay, I’m working on this my problem is In August of 2006 I got it work It was working in November of 2013 today, I’m sorry guys it’s sort of I’m sorry. It’s sort of not working very well And I’m going in with an oscilloscope. It’s the oscilloscope is there Okay, so unfortunately You can see it’s dancing around if we type a number in BAM uh I Can see that two of the scanning boards are working? I can also see that I’ve got some troubles in the arithmetic board And the logic nope I’ve got work to do the happy thing is Alongside this that Bob Reagan helped me fix.
I’ve got a second one which happily As of last night, what’s working? Not sure, it’s working now, but let me give it a try if I’m lucky Oh We’ll do all our calculations with seven decimal places. There is a stack of four Four numbers and I enter on the lowest stack, which should be brightest.
I’ll enter 20 to Enter now I have 22 oh I’m going to divide by seven seven Divided 3.14 an approximation for pi. We just showed that it divided. Let’s do a square root square root of 2/2 square root watch how long it takes, OOP? It takes a second to do a square root. Let’s actually go all the way out do it to twelve decimal places to Square root It takes the better part of a second to find the square root of two, but it does it and in 1963 People were astonished hey when I first used this in college in 1971-72. I was astonished Bring the square root of two dozen decimal places in a second Wow I don’t have to look it up I don’t have to do an expansion absolutely sweet so this machine that I’m working on I Compare voltages to this working machine, so I’m in there and You can see a hope it’s visible Brady that so now let’s do the square root of 2 1 point 1 4.
Let’s crank the decimal place back here clear entry 22 enter 7 divided And there it’s an approximation for pi a little bit of lousy You know few digits of approximation and so to repair this guy. I’ll be comparing voltages from this guy here into here and Check this out of course It’s a continuing problem November 2013 repaired ok so this guy’s working why do I work on this it’s partly out of Respect for those who came before me brilliant engineers, it’s partly out of a sense of Appreciation for their work for for their their use of the available Technology that today people will laugh at it discrete transistors I’m not sure you can buy a discrete germanium transistor anymore certainly not one. They bet made by Texas Instruments its admiration for those who came before me and of course, it’s also a wonderfully entertaining jigsaw puzzle debugging software hey I don’t need much more than a computer and a brain debugging hardware. It means understanding Not just what’s supposed to happen Understanding not just what is happening, but also understanding what Was in the mind of the people who created this the reason for For working on this isn’t oh look. I’ve got a museum piece.
No that doesn’t mean anything the reason is It teaches me gives me a sense of of Joy that I? I’m bringing to life What people who came before me gave birth to? Every time I want it, let’s try something slightly more complex, let’s set this to fourteen million six hundred Five Three one so this is fourteen million six hundred thirty seven thousand five hundred thirty one