Alan Turing’s Remarkable, Nearly-Forgotten Voice Encryption Device

June 26, 2026 by Donald Papp 14 Comments

[Popular Mechanics] has an interesting article about Alan Turing’s nearly-forgotten speech encryption device. Codenamed Delilah, it was in many ways an early form of digital encryption. It was secretly developed alongside his most famous wartime achievement of breaking the encryption used by the Nazis’ Enigma machine; itself a remarkable device we’ve covered in detail in the past.

Delilah was developed at a separate location, and Turing worked with a young electrical engineer by the name of Donald Bayley who not only helped Turing implement design concepts and theory as practical circuitry, but took copious notes of their work and discussions. His documents went up for auction in 2023, a few years after his death, and they reveal a first-hand account of their work.

SIGSALY (the name is not an acronym, by the way) was a working voice encryption system whose main drawbacks were its massive size, weight, and power requirements. [image: Wikipedia]

Back then, a vocal encryption system did exist. Bell Labs had developed SIGSALY, a seriously top-secret system that provided encrypted voice communications at the highest levels. But one of SIGSALY’s biggest drawbacks was that it was absolutely monstrous.

Delilah did the same job, but was portable and battery-powered. Delilah was three small boxes weighing around 39 kg, and it’s hard to overstate just how remarkable of a feat of miniaturization this was. However, by the time Delilah was wrapped up, the war was over and the project wound down without ever being produced or deployed in any meaningful way.

Encrypted communications is standard stuff today, but back then there was simply no need for a vocal encryption system in peacetime. The reason we know what we do today is thanks mainly to the effort Bayley put into documenting things. It’s yet another achievement by a man for whom life was far from being either easy or fair; Turing was prosecuted by his own government for “homosexual acts” and ultimately took his own life in the years following the war.

It again demonstrates that if the people involved don’t write things down while they know it, that knowledge can simply disappear. Sometimes people make the effort and the rest of us benefit, like with the Delilah project and also with the history of liquid rocket propellants — a dry-sounding topic that we assure you is anything but.

New Record Resurrects Long-Dead CD Graphics Format

June 25, 2026 by Zoe Skyforest 9 Comments

Audio CDs were the ubiquitous audio format of the 1990s. Lesser known were the extensions to the format that packaged all kinds of interesting additional data into a musical release. Now, a new record from [Aizysse Baga] has brought back some of the most quirky and obscure CD features that time and industry long forgot.

[Aizysse Baga] worked with [Adelaide] on the Divacore record, which was to be released on a mini-CD. The original plan was to include additional CD+G data, featuring artwork to go with the music. CD+G, or CD+Graphics, was often used to display synchronized lyrics for karaoke releases, and stored data in formerly-unused subcodes next to the track start, track number, and running time data. This format allowed storing a slideshow of images with a resolution of 288 x 192 with a 16 color palette.

Note the quality difference between the 16-color CD+G and the 256-color CD+EG images.

The duo got handy with art and some smart dithering to get great 16-bit artwork packed in to the audio CD release, with the aid of a custom Python encoder. CD-TEXT metadata was thrown in for good measure. Then, the existence of the more advanced CD+EG became apparent. This was a 256-color extension to the CD+G format that was backwards compatible to boot. It was a format that was barely ever implemented on any commercial releases, and very little hardware could even display it. Naturally, Divacore had to have it. Much work was done to understand the Red Book documentation on the standard and figure out how to implement even higher quality artwork for the record.

After so much work to understand and implement the CD+G and CD+EG data, the question was whether it would survive the CD reproduction process for the final release. Thankfully, the final discs came out perfectly, and the full 256-color CD+EG artwork can be seen in all its glory if you happen to play Divacore on a Sega Saturn or a super-obscure Victor VS-G2 or VS-G3. Throw it in a less-sophisticated karaoke machine or something like an Amiga CD32, and you’ll still get to see the 16-color versions for your trouble.

We love to see ancient formats brought back to life, particularly those that never got their time in the sun. If you’re working hard to resurrect something the mainstream media world has forgotten, let us know on the tipsline.

Creating Beautiful Light Shows With Soap

June 19, 2026 by Zoe Skyforest 15 Comments

We feature a lot of fun projects with LEDs and lasers and all kinds of light effects going on. Most of these are very digital. However, there are a great many ways to make beautiful lighting effects without ones and zeros. The Maelstrom Lamp from [Michele Lorenzi] is a great example of that.

*The Maelstrom Lamp is externally decorated to indicate its function.*

The concept is decidedly old-school. The lamp uses a delicate, thin soap film stretched across an aperture as its primary optical element. The varying thickness of the film across its surface leads to constructive and destructive interference when white light passes through it. This creates a kaleidoscope of color; the same effect you might have seen when an oil slick forms in a dirty puddle.

In this case, though, that effect is projected with the aid of a powerful 800-lumen flashlight and some supporting optics. [Michele]’s write-up does a great job of explaining the finer design details that maximize the vibrancy of the effect, from the waviness in the gasket that supports the soap film, to the optics that focus the torch beam.

If you’re looking for some suitably psychedelic lighting effects for your next house party, you really ought to build one of these. We’ve featured some other fun classic lighting effects before, like these wonderful bubble lamps. Continue reading “Creating Beautiful Light Shows With Soap” →

The Problem Of Making A Good Metal-To-Glass Seal

June 16, 2026 by Jenny List 22 Comments

If you’ve ever taken a close look at a vacuum tube, you’ll have seen the seals around the pins that keep everything air-tight while providing the the device’s electrical contacts. As [maurycyz] finds out, it’s not an easy process to get right.

The problem is one of both chemistry and thermal expansion, as while a good seal can be made between glass and red copper oxide, it remains very difficult indeed to stop the glass cracking on cooldown due to differing thermal expansion properties. We’re led through a variety of experiments including surface treatments and flattening the metal to a sheet, with varying pros and cons. The most successful seal on the page comes from very thin tungsten wire, though hardly the most practical conductor for a vacuum tube.

It’s a fascinating investigation for the casual reader, taking them into the properties of metal-glass bonds and the difficulties involved in making them. We have even more respect for the people who make their own tubes after reading it.

So Many Analog To Digital Converters

June 11, 2026 by Al Williams 47 Comments

An old algebra teacher used to say, “You have to take what you know and use it to get what you don’t know.” You might say the same thing about converting analog signals into digital. Computers know how to count and keep time. [Eric Explains] has a video purporting to explain “every type of analog-to-digital converter.” We aren’t sure he got every possible method, but there’s still a lot of information in the video, which you can see below.

From the flash ADC, using a ton of comparators to the successive approximation converter, which essentially plays a game of hi/lo, guessing the answer and figuring out if the real answer is higher or lower.

Continue reading “So Many Analog To Digital Converters” →

Does Your Terminal Speak Morse? This One Does

June 2, 2026 by Tyler August 7 Comments

There are a lot of single board computers on the market these days, so you can be forgiven if you missed the LuckFox Lyra. Its main claim to fame seems to be that it shares the Pi Pico’s 51 mm x 21 mm footprint while being powerful enough to run a full Linux system– or at least, it was. Now its claim to fame is as a device you can interact with no peripherals, accessing the terminal via Morse code. That’s thanks to [Gabriel Broussard Korr] and his Morstdin project, which should run on just about anything POSIX-compliant, by dint of a being a clever sh script at heart.

Of course, with most POSIX-compliant systems, you’ll need to alter the script to account for some kind of periferal to do the Morse I/O– not so on the LuckFox Lyra, which has a built-in LED and a single usable button. It actually has two buttons, but one of them is RESET and you can’t use that for anything but its intended purpose. The BOOT button, on the other hand, becomes user input after the system has started. One button, one LED? It’s almost like LuckFox designed this SBC for Morse! Admittedly we’d prefer an audible output, but adding a buzzer would detract from the purity of this implementation.

He’s had to extend the code, of course, since Samuel Morse did not expect all of the special characters you’re likely to encounter on the terminal. The resultant Programmer’s Morse, or PMorse is a straightforward extension, but [Gabriel] didn’t stop there: he’s also added a set of commands he describes as “vim-like” make using this headless device easier by doing things like deleting whole words or flash the line you’re working on so you can make sure you haven’t made any errors.

If that wasn’t enough, he’s also put an LLM on it. Because in the Year of Our Lord 2026, you apparently cannot escape the frakkin’ toasters by jumping your rag-tag fleet into the 128 MB of RAM on this tiny SBC. Still, his inclusion of Llamma.cpp does add one thing to the project: it can now claim to be the world’s smallest stand-alone chatbot. It’s also the only one that speaks Morse. That’s got to be worth some bragging rights.

[Gabriel] may have a thing for physically tiny Linux devices– his last project, which we featured, was about using Linux on old smartphones with Termux.

Thanks to [Gabriel] for the tip!

Header image credit Luckfox.

A Camera Viewfinder Makes A Great TV

May 31, 2026 by Jenny List 2 Comments

When we think of CRT camera viewfinders, most of us probably imagine the tiny CRTs you’d find in a 1980s camcorder. They’re super cute and a load of fun to play with, but they’re very much a consumer device. Professional cameras of the type you’d find in a studio had their own viewfinders, which were a lot closer to a small TV. They’re about as high quality as it gets for a monochrome CRT, and [Evan Monsma] has done the conversion to a general-purpose monitor.

On one side, this is a very straightforward hack, simply a case of tracing wires to identify the power and video pins. Given a tool battery, the monitor fires up and gives a super-sharp picture. What we like about this is the wooden base he’s made for the thing, at the same time rough-and-ready, and professional-looking from the outside. It has a routed space for the cables, and once mounted flush with the monitor base and given a bit of wood stain, it looks almost as though it was manufactured that way.

It’s likely most of us won’t find a broadcast viewfinder in the trash, instead settling at best for a little Chinese portable TV. But it’s still interesting to see these unusual devices. Perhaps it might make a good cyberdeck.

Continue reading “A Camera Viewfinder Makes A Great TV” →