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.”

Ring

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.

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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.

 

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