Technology
RotaryCell project details method for converting vintage rotary phones to cellular operation
An open-source repository documents a working prototype that enables unmodified rotary telephones to place calls using an ESP32-S3 and an LTE modem.
The short version
- An open-source hardware and software project called RotaryCell enables unmodified vintage rotary telephones to operate over cellular networks.
- The system uses a LilyGO ESP32-S3 board with an A7670 cellular modem and a Silvertel subscriber-line interface to drive the phone's native mechanical ringer, pulse dialer, and handset.
- A hand-wired prototype is functional, while custom printed circuit boards ordered in late August 2026 await physical assembly and validation.
Key facts
- The RotaryCell system mounts electronics reversibly inside an original telephone casing without cutting or altering vintage components.[Hacker News]
- Hardware components include a LilyGO T-A7670G-S3 board housing an ESP32-S3 controller and an A7670 modem, alongside a Silvertel AG1171 subscriber-line interface.[Hacker News]
- The project's firmware version 0.10.4 supports pulse dialing, switch-hook detection, bell ringing, call handling, tone generation, and over-the-air updates.[Hacker News]
- Integrated PCB designs for audio conditioning, hardware resets, and the AG1171 carrier were ordered from JLCPCB in late August 2026.[Hacker News]
- The project repository is licensed under the MIT License and includes wiring references, schematics, and Gerber packages.[Hacker News]
What remains uncertain
- The functionality and reliability of the custom integrated PCBs remain unverified until assembled boards undergo testing.[Hacker News]