Ramazan Eren Arslan turned a Deutsche Bundespost FeTAp 791 rotary telephone into a voice assistant, with the build documented on Hackster.io. Lift the handset and talk, and Google Gemini answers through the original earpiece.

A Raspberry Pi 3B sits inside the phone where the original PCB used to be. The hook switch wires to GPIO 17 so the Pi knows when the handset is lifted. The rotary dial pulses go to GPIO 22, and dialing a number selects the assistant language. Audio runs through a USB sound card.

Arslan expected to replace the handset parts, since the carbon microphone was not meant to work with a sound card built for electret mics. Both the microphone and the speaker worked when connected directly. The audio quality is poor, which he counts as part of the nostalgia. He notes that AI did much of the coding and documentation, so bugs are likely.

See more at hackster.io and content on GitHub.