Tag Archives: Rotary Phone

Hacking a rotary phone into a recorder and playback machine

Rotary X turns an old-school device into a modern-day question and answer machine.

For you youngsters out there, touch tone phones were an interesting piece of technology that used a rotary dial to create a certain number of on-off pulses. This told the phone company what phone number you, literally, dialed. Though this technology was phased out beginning in the 1960s, these resilient devices could still be found many years later. They can also be purchased and turned into something else. As Maker Lizzy Brooks puts it, “Like a lot of analog technology, rotary phones operate with a series of high/low switches that can easily be wired into an Arduino for programming adventures.”


In this case, Brooks is referring to her Rotary X question and answer machine. The guts of this phone are hooked up to an Arduino Uno (ATmega328) which interfaces with a hidden PC to state questions and record responses, controlled by the pulses generated by the rotary dial. Or, as the video below puts it, it’s “magic.”

In addition to wiring the dial and hook switch up to the Arduino, Brooks had to create a new electromagnet for the ringer by simply wrapping insulated wire around the bolt that held the orignal magnet. The microphone and speaker in the phone’s headset were replaced with a microphone scavenged from an earbud set, and a headphone speaker. Brooks notes that, although she used a PC, one could probably use an Arduino audio shield and forgo the PC altogether.


Looking ahead, the Maker is also hoping to add a sensor so it can ring whenever someone approaches, and to connect to the Internet so that it can react to various API data (like ring as you receive a tweet).

If you’d like to try something like this yourself, the Rotary X Arduino and Processing files are available online, and more info on wiring these old phones can be found on Andrew Stella’s “audio_maelstrom” blog.


Turning an old rotary phone into mobile handset

Project iRotary is one man’s quest to turn an old rotary phone into a mobile device.

When Stavros Korokithakis was refused a landline in his new office space by the phone company, he decided to channel his inner anger by modding the inner workings of an antiquated rotary phone into a modern-day mobile handset. Not to mention, being a vexed person and all, the Maker sorely missed the tactile sensation of slamming the phone on someone’s face — something that would once again be possible.


“My ultimate goal with this is to be able to take it out to the coffee shop, place it on the table and look crazy because I’m talking on an old-timey rotary phone with no cable even coming out of it,” he writes.

To accomplish this, the Maker used an Arduino, a GSM shield and a 25-year-old Seimens rotary phone, along with some open-source code. The project itself took just two days from start to finish, and only set him back about $150. Now completed, Korokithakis’s device connects to a mobile network via its shield, while the Arduino allows him to make and receive calls. That’s pretty much it — no web browsing, no SMS messages, no Facebooking.

Korokithakis did remove its bell (responsible for that infamous brngggg-ing soundin order to make room for the handful of electronic components inside the orange shell. A short Arduino script was also employed to convert the pulse dial method of the rotary pad to actual digital numbers that can be dialed by the system. The sketch is set up so that after the 10th digit is read, the call is placed through the GSM shield and its associated library.


Beyond that, the retrofitted gadget features an authentic hang-up button and an indicator LED to reveal when the phone is booting or ringing. In order to connect these controls, the Maker developed an event-driven architecture with the help of a little programming that enables it to ignore inputs when at rest, answer calls when lifted from the hook, and of course, end calls when slammed down.

“Achieving this is easy with a state machine. That simply means that there’s one variable that always contains the current state of the phone, i.e. whether it’s idle, in a call, ringing, dialing, etc. Then, any events that pop up (such as ‘button pressed’) can just check what state the phone is in, and either perform the necessary action or do nothing,” Korokithakis notes.

Designed with portability in mind, the DIY handset is powered through a small 5V battery and a USB charging circuit. As for what the future holds for this device, Korokithakis hints at a possible Kickstarter campaign in the coming weeks. Until then, those wishing for one of their own are in luck. The Maker has made his project and its code available on Github.