A Home Payphone

June 4, 2022 by Al Williams 9 Comments

We can’t condone what [Bertrand] did as a kid to make him a fan of payphones, but we get his desire to have one of his own in his home. Even if you don’t want one yourself, he’s got some good shots of the insides of a real phone that came from a casino in Vegas.

As you might expect, these phones were built like tanks. They obviously took a lot of abuse. We had to wonder how much each one cost to produce back in the day. Cleaning up an old phone and getting it to work doesn’t seem like a big effort, but there’s one thing we didn’t think about. Turns out there is a backplate that holds the 50-pound phone up and you need special studs that screw into the phone to hold it up while you put screws through both pieces.

He did connect the phone successfully to a regular phone jack, but his goal was to let his 5-year-old use the phone so he decided to actually wire it to a phone line simulator that just provides a connection between two phones.

New York City recently ripped out its last payphones. They were replaced with multipurpose kiosks, but there are still privately-owned payphones in the city. Of course, you can always use an old payphone as a platform for a different project.

NYC Hangs Up Its Last Pay Phone

May 26, 2022 by Kristina Panos 48 Comments

It was a melancholy Monday this week in the Big Apple as the last public payphone was uprooted from midtown Manhattan near Times Square and hauled away like so much garbage. That oughta be in a museum, you’re thinking, if you’re anything like us. Don’t worry; that’s exactly where the pair is headed.

This all started in 2014 when mayor de Blasio pledged to move the concept of street-level public utility into the future. Since then, NYC’s payphones have been systematically replaced with roughly 2,000 Link Wi-Fi kiosks that provide free domestic phone calls, device charging, and of course, Internet access. They also give weather, transit updates, and neighborhood news.

There are still a few private payphones around the city, so Superman still has places to change, and Bill and Ted can continue to come home. But if you need to make a phone call and have nowhere to turn, a Link kiosk is the way to go.

Although your Cap’n Crunch whistle hasn’t worked in decades, it’s still a sad day in history for the Jolly Wrencher, whose maiden message was about ye olde red boxen. We’re already seeing pay phones live on as art, so that’s a good sign.

Images via PIX11 and CBS News

Build A Prop For A TV Premiere? Stranger Things Have Happened

May 25, 2022 by Kristina Panos 7 Comments

Some guys get all the breaks. [Guy Dupont] had the honor of building a working, interactive wall-mount landline phone for the red carpet premiere of a certain TV show. The phone was to be an Easter egg inside an 80s-style pizzeria set. About every two minutes the phone would ring, and anyone brave enough to answer would be greeted with either a fake pizza order, an old answering machine message, or a clip from The Show That Cannot Be Mentioned.

So the phone doesn’t work-work, but the nostalgia is strong — picking up the receiver when the phone isn’t ringing results in a dial tone, and button pushing leads to the busy signal. Those old pleasant-but-stern operator recordings would have been cool, but there was only so much time. (Your call cannot be completed as dialed. Please check the number and try again.)

[Guy] used a SparkFun RP2040 to handle input from the DTMF keypad and play the tones, the dial and busy signals, and the various recordings into the ear of the receiver.

Instead of messing around with the high voltage needed to drive the original ringer and bell, [Guy] used a small speaker to play the ringing sound. Everything runs on eight AAs tucked under the keypad, which is stepped down to 5 V.

This project was built under fairly dramatic duress, which makes it that much more exciting to watch the build video after the break. With just five days to get the phone working and in the mail, [Guy] holed up on the floor of his office, his messy mid-move refuge from a house plagued by COVID. Unfortunately, the whole pizzeria thing fell through, so [Guy]’s phone will not get to have its moment on the red carpet. But at least it’s on the site that’s black and white and read all over.

[Guy] is no stranger to the old tech/new spec game. Remember that time he shoehorned Spotify into an iPod Classic?

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How A Smartphone Is Made, In Eight “Easy” Blocks

May 9, 2022 by Matthew Carlson 21 Comments

The smartphone represents one of the most significant shifts in our world. In less than thirteen years, we went from some people owning a dumb phone to the majority of the planet having a smartphone (~83.7% as of 2022, according to Statista). There are very few things that a larger percentage of people on this planet have. Not clean water, not housing, not even food.

How does a smartphone work? Most people have no idea; they are insanely complicated devices. However, you can break them down into eight submodules, each of which is merely complex. What makes them work is that each of these components can be made small, at massive economies of scale, and are tightly integrated, allowing easy assembly.

So without further ado, the fundamental eight building blocks of the modern cellphone are: the application processor, the baseband processor, a SIM card, the RF processor, sensors, a display, cameras & lenses, and power management. Let’s have a look at them all, and how they fit together.

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Several relays and switches mounted on a metal frame

The Simplest Electro-Mechanical Telephone Exchange That Actually Works

April 14, 2022 by Robin Kearey 34 Comments

While rarely seen by users, the technology behind telephone exchanges is actually quite interesting. In the first hundred or so years of their existence they evolved from manually-operated switchboards to computer-controlled systems, but in between those two stages was a time when dialling and switching was performed electromechanically. This was made possible by the invention of the stepping switch, a type of pulse-operated relay that can connect a single incoming wire to one of many outgoing wires.

Public telephone exchanges contained hundreds of these switches, but as [dearuserhron] shows, it’s possible to make a smaller system with way fewer components: the Cadr-o-station is built around one single stepper switch. Although it looks rather complicated, the only other components are a bunch of ordinary 24 V relays and a few power supplies. Together they make up a minimal telephone exchange that connects up to ten handsets.

It doesn’t have all the functionality of a larger system however, as only a single voice circuit is made to which all phones are automatically connected. Still, it does allow users to dial a number and let the other phone ring, which might be good enough for a home or indeed the hackerspace where it’s currently sitting. It’s also a fine demonstration of how relatively simple technology can be applied to make a surprisingly complex system.

[dearuserhron] wrote an in-depth article on the workings of electromechanical telephone exchanges, which might come in helpful to anyone who’d like to design such a system for their own home. For a more general introduction into analog phone technology, check out our analysis of a 1970s rotary telephone.

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A Custom Radio And Telephone System For Glider Winch Operators

March 1, 2022 by Robin Kearey 16 Comments

While gliding might be the most calm and peaceful way of moving through the air, launching a glider is a rather noisy and violent process. Although electric winches do exist, most airfields use big V8-powered machines to get their gliders airborne. [Peter Turczak] noticed that the winch operators at his airfield often had to juggle multiple communication channels while pressing buttons and moving levers, all with the deafening roar of a combustion engine right next to them. To make their life easier, he built a single communication device that combines multiple radio inputs and an analog telephone .

A stack of circuit boards next to an old phone ringer — The inside of the cabinet. Note the classic phone ringer

The main user interface is a sturdy headset that dampens engine noise significantly. This headset is connected to a cabinet that contains several modules connecting to different audio sources: an analog telephone line, an aircraft radio receiver, a PMR handheld radio, and even a music source in case the other lines are quiet. The system contains automatic switchover circuits based on a priority system, ensuring that important messages are never missed.

The electronic design is based on classic analog components like NE5532 and TL084 op amps, all mounted on small, custom-made PCBs. Audio transformers are used to avoid ground loops between the various signal sources while relays mute sources that are not prioritized. To ensure seamless compatibility with the telephone network, [Peter] used components from old desk phones, including line transformers, a DTMF keypad and even a mechanical ringer. His blog post is full of details that will be of interest to anyone working with op amps and audio, such as how to stabilize an amplifier that has significant wiring capacitance on its input.

At heart this whole project is “just” an audio mixer, although optimized for a very specific purpose. But designing even a simple mixer is by no means an easy task, as we reported a few years back. If you’re more into winches, you’ll be delighted to find that smaller ones can also be used for sledding and even wakeboarding.

An Up-To-Date Development Environment For The Nokia N-Gage

January 27, 2022 by Jenny List 18 Comments

One of the brave but unsuccessful plays from Nokia during their glory years was the N-Gage, an attempt to merge a Symbian smartphone and a handheld game console. It may not have managed to dethrone the Game Boy Advance but it still has a band of enthusiasts, and among them is [Michael Fitzmayer] who has produced a CMake-based toolchain for the original Symbian SDK. This is intended to ease development on the devices by making them more accessible to the tools of the 2020s, and may serve to bring a new generation of applications to those old Nokias still lying forgotten in dusty drawers.

In much of the public imagination, the invention of the smartphone came with the release of the first Apple iPhone in 2007. Hackaday readers will of course trace the smartphone back much further than that to an original IBM prototype, and will remind any doubters that the Nokias which the iPhone vanquished were very successful smartphones without any of Cupertino’s magic in sight. Nokia’s tragedy was that they appeared not to understand what they had in Symbian, and released a bewildering array of devices intended to satisfy every possible market without recognizing that the market they needed to serve was their customers being easily able to run the apps of their choice on the things.

Symbian itself has long ago become a piece of abandonware, but during its chequered history there was a period in which an open-source version was released. It would be nice to think that projects such as this one might revive interest in this capable yet forgotten operating system, as with the passage of a decade the cost of hardware which might run it has fallen to the point of affordability. Does anyone want to relive the 2000s?

Header image: Evan-Amos, Public domain.