Soviet-Era Auto Dialler Uses Magnetic Rope Core Memory

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We’ve seen a few interesting magnetic core memories on these fine pages over the years, but we don’t recall seeing too many user programmable magnetic core memory devices. This interesting Russian telephone auto dialer in its day would have been a very useful device, capable of storing and dialing forty user programmable 7-digit numbers. [mikeselectricstuff] tore into one (video, embedded below), and found some very interesting tech. For its era, this is high technology stuff. Older Russian tech has a reputation for incredibly ingenious use of older parts, that can’t be denied. After all, if it works, then there’s no need to change it. But anyway, what’s interesting here is how the designers decided to solve the problem of programming and recalling of numbers, without using a microprocessor, by using discrete logic and core rope memory.

This is the same technology used by the Apollo Guidance Computer, but in a user configurable form, and obviously much smaller storage capacity. The core array consists of seven, four-bit words, one word per telephone digit, which will be read out sequentially bottom to top. The way you program your number is to take your programming wire, insert it into the appropriate hole (one row related to numbers 1-20, the other row is shifted 1-20 for the second bank) and thread it along the cores in a weave type pattern. Along the way, the wire is passed through or bypasses a particular core, depending upon the digit you are coding for. They key for this encoding is written on the device’s lid. At the end, you then need to terminate the wire in the matching top connector, to allow the circuit to be completed.

As far as we can tell, the encoding is a binary sequence, with a special ‘stop’ code to indicate telephone numbers with less than seven digits. We shall leave further analysis to interested parties, and just point you at the Original manufacturer schematics. Enjoy!

Of course we’re not just going to mention rope core memory and the AGC without linking to a fantastic article about the very same, and if that’s wetting your appetite for making a rope core memory, here’s a little thing about that too!

12 thoughts on “Soviet-Era Auto Dialler Uses Magnetic Rope Core Memory”

    1. I’m guessing that Hackaday writers have a pool of tips they can all draw from, and sometimes a double select happens.
      So, from time to time, someone besides [Lewin] will do an automotive article, someone besides [Jenny] does an article on metal smithing, and so on.

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  2. Did they really need speed dialers? Obviously just for the party leaders.

    In the seventies, there were some projects in ham magazines using cores. Most obvious were some keyboards, for CW and rtty, to encode the characters, so they weren’t programmable.

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    2. I think the main benefit of these devices was as a memory aid — being able to store frequently called numbers and redial them easily with a button or two. It was not necessarily about the speed savings you’d experience by pressing fewer buttons. Although I suppose, if you were trying to dial into a radio station prize contest or by concert tickets, a situation where the lines were clogged with callers, the redial speed might give you an edge over those dialing (or punching) with mere biological digits.

      The first company I worked for back in the 1980s installed a used PBX that looked like it was from the 1970s. Not only could your desk phone store a dozen or so phone numbers, there was a bank of 100 phone numbers that was company-wide accessible to all. Not core memory, but OTP PROM chips. With our cell phones and integrated address books, we don’t need this kind of technology as much these days.

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