We've all been there: A meeting goes sideways and you really wish you could physically slam the phone down and walk away. Maker Stavros Korokithakis knows that feeling well, so he took an old rotary phone and turned it into a device that can dial into - and hang up on - video calls in a decidedly retro fashion.
Armed with an old Siemens rotary phone, "30 percent of the knowledge required, and 100 percent of the underestimation of how hard the other 70 percent would be," per Korokithakis' writeup of his build, the Greek software developer proceeded to build a device that can dial - meeting ID digit by meeting ID digit - into calls, speak and listen through the receiver, and disconnect from meetings by hanging up.
Korokithakis modified the old Siemens phone by taking a two-dollar USB sound card, tearing it apart and wiring the handset up to it, and connecting the card to a USB hub. That hub, in turn, was wired to a USB hub that was connected to a Raspberry Pi RP2040 microcontroller programmed not only to send common keystroke combinations that end calls on collaboration software (like Ctrl+Shift+E on Zoom or Ctrl+W on Meet), but also to listen for the GPIO pin that is pulled when the receiver is hung up and listen to the rotary switch for dialing meeting IDs.
The internals of Korokithakis' Siemens rotary online meeting phone. The RP2040 that handles dialing and picking/hanging up is inside the phone under the electrical tape, which feeds to the USB hub, which in turn is wired to the USB sound card that attaches to the receiver cord. Image: Stavros Korokithakis - Click to enlarge
"The rotary dial is similarly a second switch, one that opens and closes very quickly, a number of times equal to the number you just dialed," Korokithakis wrote. "The software on the RP2040 just counts these opens and closes, waits a few milliseconds to see if there are any more of them, and, if not, simulates a keyboard typing the number it counted."
The Register caught up with Korokithakis to chat about the project and get a first-hand demonstration. The device worked, and it was noticeable how much difference there was in the sound quality between the modern headset Korokithakis was using for most of the call and the Siemens receiver. When switched to the latter, it was obvious we were listening to audio transmitted through a piece of analog hardware manufactured in the 1970s.
Korokithakis demonstrates his rotary meeting phone during our chat - Click to enlarge
"I have used it to dial into meetings," Korokithakis told us, noting that he usually only subjects his coworkers to his maker escapades. "People know me and they know that I do this crap all the time and so they're just kind of like, oh, yes, of course, another one of the things."
"Usually they laugh and ask, 'are you actually talking through this thing?' They're surprised when I say yes," Korokithakis added.
This is Korokithakis' latest rotary phone experiment, but it's not his first one. Prior to creating a device he could use to dial into virtual meetings, he took another old rotary phone - this time a flashy orange device - and turned it into a mobile phone he dubbed the iRotary.
That was a much more difficult project, Korokithakis explained, but in the end, he had a device he was able to take out and about to make and take calls.
"I took it out to a cafeteria and I was talking to my parents," the Greek maker explained. "Somebody came to the table and asked, 'Are you absolutely talking on this? Is it actually a mobile phone?' I said, 'Yeah, I made it,'" he explained. "It's a good conversation starter."
That build, while being more complicated due to having to wire in a cellular modem, SIM card, and battery, still works relatively simply. The ringer isn't connected, but it does flip an indicator to red to notify Korokithakis that a call is coming in, and, other than that, it just spins the rotor to dial a number. Unlike the meeting phone, however, the code for the iRotary stores the entire 10-digit number (the normal length of a phone number in Greece) before dialing so that it works with modern cellular architecture.
One of Korokithakis' favorite vintage features about the old rotary phones he experimented with, he told us, is the fact that they have sidetone (i.e., the microphone transmits what it picks up to the speaker so you can hear yourself), which still worked in his experiments, albeit better on the iRotary than the meeting phone.
With modern phones, "you keep yelling because your brain thinks they can't hear you because you're muffled," Korokithakis explained. "This plays the audio through the earpiece, so I know I can be heard, which is very satisfying."
For those worried that he destroyed a pair of vintage rotary phones, there's no need for concern, Korokithakis explained in his blog posts and in our call: Unlike modern built-to-fail electronics, those old rotary devices were not only simple and built to be cracked open (both devices even included a complete schematic on the inside, Korokithakis told us), there wasn't a lick of solder in sight, so he didn't have to make any permanent modifications.
Take the Siemens meeting phone, for instance: Every wire in the device is connected to the circuit board with a connector that can be removed and replaced if, say, a wire goes bad. What that meant for Korokithakis' tinkering is that he simply had to 3D print his own connector to attach his components. While both devices are still wired up with his custom builds, it would be entirely possible for him to remove his modifications and be left with a pair of stock rotary phones that could take up space on a shelf instead of being used for such interesting projects.
If you happen to have a spare rotary phone or two lying around and want to try either of Korokithakis' builds for yourself, the code for both the meeting phone and the iRotary are available on Github.
As for build instructions, you'll have to refer to Korokithakis' blog posts and your own know-how to sort that out. ®
Source: The register