Sometimes, you find the coolest things at antique stores. While on vacation last year in Maine, I came across a Morse model 4-C telegraph relay (circa 1900). It looked complete, so I bought it to add to my collection of cool historical tech. Once the contacts were cleaned off and the settings adjusted, it turned out to work quite well.
(Oxidation is an insulator, so vintage “patina” or no, it had to go.)
Here’s a clip of it sending “HELLO, WORLD” in Morse code.
To a computer engineer, vintage relays are a fascinating tease of possible alternate timelines. With even as simple a device as this (a pair of electromagnets moving a contactor) you have the basic building elements of a computer, provided a NC contact was added. And there’s even a spare contact screw for one.
With such a device, you can build logic gates. By combining them, you can make flip-flops, which can themselves be combined into memory devices, registers, counters, and all of the other pieces needed for a computer. We could have had computers in the 1800s!
…And not only does it still work, it’s crazy efficient for an electromechanical device! It will strike at about 2.5V (depending on settings), and draws only 25mA at that voltage. If I weren’t running it loose and loud to get that nice clicking sound for demonstrations, it could probably be driven directly by a microcontroller pin (or two of them ganged, worst case.) The whole works, in fact, is powered from a USB port! (The diode across the coil is to snub electrical noise when the coil is depowered.)
It’s kind of surprising to see such efficiency in a device that was already old enough to graduate high school around the time my grandparents were born. It’s a reminder that, although earlier eras didn’t have all of our technological knowledge, they still very much had competent engineers who often came up with amazing solutions, even with limited technology.
It’ll make a great first exhibit for the new Mini Museum of Computing History that I’m making.
