It’s fair to say that there can’t be many developers who have found the need for a rotary telephone dial as a peripheral for their Linux computer, but in case you are among them you might find [Stefan Wiehler]’s kernel driver for rotary dials to be of use.

It’s aimed at platforms such as systems-on-chip that have ready access to extra GPIOs, of which it will need a couple to service the BUSY and PULSE lines. There are full set-up instructions, and once it’s in place and configured it presents the dial as though it were a number pad.

We like this project, in fact we like it a lot. Interfacing with a dial is always something we’ve done with a microcontroller though, so it will be interesting to see whether it finds a use beyond merely curiosity. We can already see a generation of old-school dial IP phones using Linux-capable dev boards. He leaves us with a brief not as to whether Linus Torvalds would see it as worthy of mainline inclusion, and sadly however much we want things to be different, we agree that it might be wishful thinking.

If you’d like to use a dial phone, there can be simpler ways to do it.

Header: Billy Brown, CC BY 2.0 .

At the dawn of the PC, IBM provided the Basic Input Output System (BIOS). It took care of bringing the machine up, and exposed a series of software hooks for the hardware. Over the years the BIOS and its updated descendants served us well, but as we entered a 64-bit world its limitations began to show.

The replacement was the Unified Extensible Firmware Interface or UEFI, and the chances are you’re viewing this on a machine which uses it in some capacity. But what if you only have UEFI and need BIOS to run a piece of older software? Never fear, because here’s CSMWrap, which brings it back, just for you.

Under the hood it’s a wrapper for the SeaBIOS compatibility support module, doing the work of setting up the memory mapping such that it will load, and ensuring that other services such as the VGA BIOS are loaded. As it stands it can boot FreeDOS and some older Windows versions under UEFI in QEMU, and it’s claimed also run on real hardware. We don’t often need to run DOS on our 2025 machine, but it’s neat to know we can.

Meanwhile if the BIOS interests you, know that there’s also an open source BIOS for the earliest of PCs.

BIOS header image: Thomas Schanz, CC BY-SA 4.0.

If you ask someone for a piece of received opinion about Bernese mountain dogs, the chances are that the tale of their carrying barrels of brandy round their necks for the revival of those lost in the snow. It’s a story of uncertain provenance and may indeed be a myth, but that hasn’t stopped [Saren Tasciyan] 3D printing one for their faithful hound. In its own way it too is a saviour, for as well as a small camera, it carries a supply of dog poop bags.

It’s a two part print, held together with strong magnets. Waterproofing is achieved using liberal quantities of hot glue. There’s a protrusion on one side designed to take an action camera for a dog’s-eye-view of the world. The files are downloadable, so your pooch can have one too if you like. We are wondering whether a couple of miniatures of brandy might just fit in there as well.

It’s is part of the 2025 Pet Hacks contest, so if this has whetted your appetite, expect more. If your dog carries around something you’ve made, how about making it an entry of your own?

Part of the charm of having a cat in your life is that by their nature these animals are very interactive. They will tell you in no uncertain terms when something in their lives needs attention, for example when their water dish is empty. But why not give them a drinking fountain all of their own? It’s what [supermarioprof] did for their adorable ginger cat [Piki Piki], providing a cat-operated trickle of water on demand.

It’s a simple enough device in its operation, but very well constructed. There’s a small basin with a train, and a water cistern valve operated by the cat placing a paw on a lever. This starts a trickle of water, from which they can lap as much as they like.

The physical construction comes courtesy of some laser-cut ply, and what looks like some 3D print work. It’s certainly easy to operate for the cat, and has worked reliably for a few years now.

This project is part of the 2025 Pet Hacks contest, so expect to see more in the same vein. If your cat’s life is improved by one of your projects, consider making an entry yourself!

There was a period in the 1990s when it seemed like the personal data assistant (PDA) was going to be the device of the future. If you were lucky you could afford a Psion, a PalmPilot, or even the famous Apple Newton — but to trap the unwary there were a slew of far less capable machines competing for market share.

[Nick Bild] has one of these, branded Rolodex, and in a bid to make using a generative AI less alluring, he’s set it up as the interface to an LLM hosted on a Raspberry Pi 400. This hack is thus mostly a tale of reverse engineering the device’s serial protocol to free it from its Windows application.

Finding the baud rate was simple enough, but the encoding scheme was unexpectedly fiddly. Sadly the device doesn’t come with a terminal because these machines were very much single-purpose, but it does have a memo app that allows transfer of text files. This is the wildly inefficient medium through which the communication with the LLM happens, and it satisfies the requirement of making the process painful.

We see this type of PDA quite regularly in second hand shops, indeed you’ll find nearly identical devices from multiple manufacturers also sporting software such as dictionaries or a thesaurus. Back in the day they always seemed to be advertised in Sunday newspapers and aimed at older people. We’ve never got to the bottom of who the OEM was who manufactured them, or indeed cracked one apart to find the inevitable black epoxy blob processor. If we had to place a bet though, we’d guess there’s an 8051 core in there somewhere.

It was such an innocent purchase, a slightly grubby and scuffed grey plastic box with the word “P O L A R O I D” intriguingly printed along its top edge. For a little more than a tenner it was mine, and I’d just bought one of Edwin Land’s instant cameras. The film packs it takes are now a decade out of production, but my Polaroid 104 with its angular 1960s styling and vintage bellows mechanism has all the retro-camera-hacking appeal I need. Straight away I 3D printed an adapter and new back allowing me to use 120 roll film in it, convinced I’d discover in myself a medium format photographic genius.

But who wouldn’t become fascinated with the film it should have had when faced with such a camera? I have form on this front after all, because a similar chance purchase of a defunct-format movie camera a few years ago led me into re-creating its no-longer-manufactured cartridges. I had to know more, both about the instant photos it would have taken, and those film packs. How did they work?

A Print, Straight From The Camera

In conventional black-and-white photography the film is exposed to the image, and its chemistry is changed by the light where it hits the emulsion. This latent image is rolled up with all the others in the film, and later revealed in the developing process. The chemicals cause silver particles to precipitate, and the resulting image is called a negative because the silver particles make it darkest where the most light hit it. Positive prints are made by exposing a fresh piece of film or photo paper through this negative, and in turn developing it. My Polaroid camera performed this process all-in-one, and I was surprised to find that behind what must have been an immense R&D effort to perfect the recipe, just how simple the underlying process was.

My dad had a Polaroid pack film camera back in the 1970s, a big plastic affair that he used to take pictures of the things he was working on. Pack film cameras weren’t like the motorised Polaroid cameras of today with their all-in-one prints, instead they had a paper tab that you pulled to release the print, and a peel-apart system where after a time to develop, you separated the negative from the print. I remember as a youngster watching this process with fascination as the image slowly appeared on the paper, and being warned not to touch the still-wet print or negative when it was revealed. What I was looking at wasn’t a negative printing process as described in the previous paragraph but something else, one in which the unexposed silver halide compounds which make the final image are diffused onto the paper from the less-exposed areas of the negative, forming a positive image of their own when a reducing agent precipitates out their silver crystals. Understanding the subtleties of this process required a journey back to the US Patent Office in the middle of the 20th century.

It’s All In The Diffusion

It’s in US2647056 that we find a comprehensive description of the process, and the first surprise is that the emulsion on the negative is the same as on a contemporary panchromatic black-and-white film. The developer and fixer for this emulsion are also conventional, and are contained in a gel placed in a pouch at the head of the photograph. When the exposed film is pulled out of the camera it passes through a set of rollers that rupture this pouch, and then spread the gel in a thin layer between the negative and the coated paper. This gel has two functions: it develops the negative, but over a longer period it provides a wet medium for those unexposed silver halides to diffuse through into the now-also-wet coating of the paper which will become the print. This coating contains a reducing agent, in this case a metalic sulphide, which over a further period precipitates out the silver that forms the final visible image. This is what gives Polaroid photographs their trademark slow reveal as the chemistry does its job.

I’ve just described the black and white process; the colour version uses the same diffusion mechanism but with colour emulsions and dye couplers in place of the black-and-white chemistry. Meanwhile modern one-piece instant processes from Polaroid and Fuji have addressed the problem of making the image visible from the other side of the paper, removing the need for a peel-apart negative step.

Given that the mechanism and chemistry are seemingly so simple, one might ask why we can no longer buy two-piece Polaroid pack or roll film except for limited quantities of hand-made packs from One Instant. The answer lies in the complexity of the composition, for while it’s easy to understand how it works, it remains difficult to replicate the results Polaroid managed through a huge amount of research and development over many decades. Even the Impossible Project, current holders of the Polaroid brand, faced a significant effort to completely replicate the original Polaroid versions of their products when they brought the last remaining Polaroid factory to production back in 2010 using the original Polaroid machinery. So despite it retaining a fascination among photographers, it’s unlikely that we’ll see peel-apart film for Polaroid cameras return to volume production given the small size of the potential market.

Hacking A Sixty Year Old Camera

So having understood how peel-apart pack film works and discovered what is available here in 2025, what remains for the camera hacker with a Land camera? Perhaps the simplest idea would be to buy one of those One Instant packs, and use it as intended. But we’re hackers, so of course you will want to print that 120 conversion kit I mentioned, or find an old pack film cartridge and stick a sheet of photographic paper or even a Fuji Instax sheet in it. You’ll have to retreat to the darkroom and develop the film or run the Instax sheet through an Instax camera to see your images, but it’s a way to enjoy some retro photographic fun.

Further than that, would it be possible to load Polaroid 600 or i-Type sheets into a pack film cartridge and somehow give them paper tabs to pull through those rollers and develop them? Possibly, but all your images would be back to front. Sadly, rear-exposing Instax Wide sheets wouldn’t work either because their developer pod lies along their long side. If you were to manage loading a modern instant film sheet into a cartridge, you’d then have to master the intricate paper folding arrangement required to ensure the paper tabs for each photograph followed each other in turn. I have to admit that I’ve become fascinated by this in considering my Polaroid camera. Finally, could you make your own film? I would of course say no, but incredibly there are people who have achieved results doing just that.

My Polaroid 104 remains an interesting photographic toy, one I’ll probably try a One Instant pack in, and otherwise continue with the 3D printed back and shoot the occasional 120 roll film. If you have one too, you might find my 3D printed AAA battery adapter useful. Meanwhile it’s the cheap model without the nice rangefinder so it’ll never be worth much, so I might as well just enjoy it for what it is. And now I know a little bit more about his invention, admire Edwin Land for making it happen.

Any of you out there hacking on Polaroids?

The life of a Hackaday writer often involves hours spent at a computer searching for all the cool hacks you love, but its perks come in not being tied to an office, and in periodically traveling around our community’s spaces. This suits me perfectly, because as well as having an all-consuming interest in technology, I am a lifelong rail enthusiast. I am rarely without an Interrail pass, and for me Europe’s railways serve as both comfortable mobile office space and a relatively stress free way to cover distance compared to the hell of security theatre at the airport. Along the way I find myself looking at the infrastructure which passes my window, and I have become increasingly fascinated with the power systems behind electric railways. There are so many different voltage and distribution standards as you cross the continent, so just how are they all accommodated? This deserves a closer look.

So Many Different Ways To Power A Train

In Europe where this is being written, the majority of main line railways run on electric power, as do many subsidiary routes. It’s not universal, for example my stomping ground in north Oxfordshire is still served by diesel trains, but in most cases if you take a long train journey it will be powered by electricity. This is a trend reflected in many other countries with large railway networks, except sadly for the United States, which has electrified only a small proportion of its huge network.

Of those many distribution standards there are two main groups when it comes to trackside, those with an overhead wire from which the train takes its power by a pantograph on its roof, or those with a third rail on which the train uses a sliding contact shoe. It’s more usual to see third rails in use on suburban and metro services, but if you take a trip to Southern England you’ll find third rail electric long distance express services. There are even four-rail systems such as the London Underground, where the fourth rail serves as an insulated return conductor to prevent electrolytic corrosion in the cast-iron tunnel linings.

As if that wasn’t enough, we come to the different voltage standards. Those southern English trains run on 750 V DC while their overhead wire equivalents use 25 kV AC at 50Hz, but while Northern France also has 25 kV AC, the south of the country shares the same 3 kV DC standard as Belgium, and the Netherlands uses 1.5 kV DC. More unexpected still is Germany and most of Scandinavia, which uses 15 kV AC at only 16.7 Hz. This can have an effect on the trains themselves, for example Dutch trains are much slower than those of their neighbours because their lower voltage gives them less available energy for the same current.

In general these different standards came about partly on national lines, but also their adoption depends upon how late the country in question electrified their network. For example aside from that southern third-rail network and a few individual lines elsewhere, the UK trains remained largely steam-powered until the early 1960s. Thus its electrification scheme used the most advanced option, 25 kV 50 Hz overhead wire. By contrast countries such as Belgium and the Netherlands had committed to their DC electrification schemes early in the 20th century and had too large an installed base to change course. That’s not to say that it’s impossible to upgrade though, as for example in India where 25 kV AC electrification has proceeded since the late 1950s and has included the upgrade of an earlier 1.5 kV DC system.

A particularly fascinating consequence of this comes at the moment when trains cross between different networks. Sometimes this is done in a station when the train isn’t moving, for example at Ashford in the UK when high-speed services switch between 25 kV AC overhead wire and 750 V DC third rail, and in other cases it happens on the move through having the differing voltages separated by a neutral section of overhead cable. Sadly I have never manged to travel to the Belgian border and witness this happening. Modern electric locomotives are often equipped to run from multiple voltages and take such changes in their stride.

Power To The People Movers

Finally, all this rail electrification infrastructure needs to get its power from somewhere. In the early days of railway electrification this would inevitably been a dedicated railway owned power station, but now it is more likely to involve a grid connection and some form of rectifier in the case of DC lines. The exception to this are systems with differing AC frequencies from their grid such as the German network, which has an entirely separate power generation and high voltage distribution system.

So that was the accumulated observations of a wandering Hackaday scribe, from the comfort of her air-conditioned express train. If I had to name my favourite of all the networks I have mentioned it would be the London Underground, perhaps because the warm and familiar embrace of an Edwardian deep tube line on a cold evening is an evocative feeling for me. When you next get the chance to ride a train keep an eye out for the power infrastructure, and may the experience be as satisfying and comfortable as it so often is for me.

Header image: SPSmiler, Public domain.

It’s fair to say that QR codes are a technology that has finally come of age. A decade or more ago they were a little over-hyped and sometimes used in inappropriate or pointless ways, but now they are an accepted and useful part of life.

They’re not without their faults though, one of which is that despite four increasingly redundant levels of error correction, there comes a point at which a degraded QR code can no longer be read. [HumanQR] is soliciting these broken QR codes for research purposes and inclusion in an eventual open-source database, and they’ll even have a shot at repairing your submissions for you.

It’s a problem inherent to all digital media, that once the limit of whatever error correction they contain has been reached, they arrive at a cliff-edge at which they go immediately from readability to non readability. The example given in the linked article is a locator tag on a stray cat, it had been rubbed away in part. Improving its contrast, sharply defining its edges, and improving the definition of its fiducials was able to revive it, we hope leading to the cat being returned home.

The idea is that by studying enough damaged codes it should be possible to identify the means by which they become degraded, and perhaps come up with a way to inform some repair software. Meanwhile if you are interested, you might want to learn more about how they work, the hard way.

The Thinkpad line of laptops, originally from IBM, and then from Lenovo, have long been the choice of many in our community. They offer a level of robustness and reliability missing in many cheaper machines. You may not be surprised to find that this article is being written on one. With such a following, it’s not surprising that a significant effort has gone into upgrading older models. For example, we have [Franck Deng]’s new motherboard for the Thinkpad X200 and X201. These models from the end of the 2000s shipped as far as we can remember with Core 2 Duo processors, so we can imagine they would be starting to feel their age.

It’s fair to say the new board isn’t a cheap option, but it does come with a new Core Ultra 7 CPU, DDR5 memory, M.2 interfaces for SSDs alongside the original 2.5″ device, and USB-C with Thunderbolt support. There are a range of screen upgrade options. For an even more hefty price, you can buy a completely rebuilt laptop featuring the new board. We’re impressed with the work, but we have to wonder how it would stack up against a newer Thinkpad for the price.

If you’re curious to see more of the same, this isn’t the first such upgrade we’ve seen.

Thanks [Max] for the tip.

The Sinclair C5 was Sir Clive’s famous first venture into electric mobility, a recumbent electric-assisted tricycle which would have been hardly unusual in 2025. In 1985, though, the C5 was so far out there that it became a notorious failure. The C5 retains a huge following among enthusiasts, though, and among those is [JSON Alexander, who has bought one and restored it.

We’re treated to a teardown and frank examination of the vehicle’s strengths and weaknesses, during which we see the Sinclair brand unusually on a set of tyres, and the original motor, which is surprisingly more efficient than expected. Sir Clive may be gone, but this C5 will live again.

We’ve had the chance to road test a C5 in the past, and it’s fair to say that we can understand why such a low-down riding position was not a success back in the day. It’s unusual to see one in as original a condition as this one, it’s more usual to see a C5 that’s had a few upgrades.

As transport infrastructure in Europe moves toward a zero-carbon future, there remain a number of railway lines which have not been electrified. The question of replacing their diesel traction with greener alternatives, and there are a few different options for a forward looking railway company to choose from. In Germany the Rhine-Main railway took delivery of a fleet of 27 Alstom hydrogen-powered multiple units for local passenger services, but as it turns out they have not been a success (German language, Google translation.). For anyone enthused as we are about alternative power, this bears some investigation.

It seems that this time the reliability of the units and the supply of spare parts was the issue, rather than the difficulty of fuel transport as seen in other failed hydrogen transport problems, but whatever the reason it seems we’re more often writing about hydrogen’s failures than its successes. We really want to believe in a hydrogen future in which ultra clean trains and busses zip around on hydrogen derived from wind power, but sadly that has never seemed so far away. Instead trains seem inevitably to be following cars, and more successful trials using battery units point the way towards their being the future.

We’re sure that more hydrogen transport projects will come and go before either the technological problems are overcome, or they fade away as impractical as the atmospheric railway. Meanwhile we’d suggest hydrogen transport as the example when making value judgements about technology.

No doubt many readers have at times wished to try their hand at blacksmithing, but it’s fair to say that acquiring an anvil represents quite the hurdle. For anyone not knowing where to turn there’s a video from [Black Bear Forge], in which he takes us through a range of budget options.

He starts with a sledgehammer, the simplest anvil of all, which we would agree makes a very accessible means to do simple forge work. He shows us a rail anvil and a couple of broken old anvils, before spending some time on a cheap Vevor anvil and going on to some much nicer more professional ones. It’s probably the Vevor which is the most interesting of the ones on show though, not because it is particularly good but because it’s a chance to see up close one of these very cheap anvils.

Are they worth taking the chance? The one he’s got has plenty of rough parts and casting flaws, an oddly-sited pritchel and a hardy hole that’s too small. These anvils are sometimes referred to as “Anvil shaped objects”, and while this one could make a reasonable starter it’s not difficult to see why it might not be the best purchase. It’s a subject we have touched on before in our blacksmithing series, so we’re particularly interested to see his take on it.