A DIY project has demonstrated how to modernize a vintage Deutsche Bundespost FeTAp 791 rotary telephone by converting it into a functional voice assistant. The build, documented by Ramazan Eren Arslan, utilizes a Raspberry Pi 3 Model B housed within the phone's original chassis to facilitate interaction with Google Gemini 3.8 Live.
The integration relies on specific hardware modifications to bridge the gap between analog components and digital processing. The phone's hook switch is wired to GPIO 17 on the Raspberry Pi, allowing the system to detect when the handset is lifted. Meanwhile, the rotary dial pulses are routed to GPIO 22, enabling users to select their preferred language for the assistant by dialing specific numbers.
Audio input and output are managed through a USB sound card connected to the Raspberry Pi. Although Arslan initially anticipated needing to replace the handset's internal components due to compatibility concerns between the vintage carbon microphone and modern sound cards, both the original microphone and speaker functioned when connected directly. The resulting audio quality is described as poor, a characteristic the creator considers an intentional part of the nostalgic experience.
The project is designed to be adaptable to other rotary phone models, providing a template for those interested in retro-hardware modification. Arslan noted that the coding and documentation for the assistant were largely generated with the help of AI, suggesting that users may encounter bugs during implementation. Detailed instructions and project files are available for those looking to replicate the build.