RotaryCell: Making an unmodified rotary phone work over LTE with an ESP32-S3
The RotaryCell project demonstrates how to convert a vintage rotary telephone into a portable cellular device using an ESP32-S3 and a cellular modem. The design is non-destructive, allowing the original hardware to remain intact while adding modern connectivity.
Why it matters
It showcases creative hardware engineering and the repurposing of legacy technology for modern use cases.
RotaryCell converts a traditional rotary telephone into a self-contained, battery-powered, portable cellular telephone without modifying the original telephone .
The design continues to use the original handset, rotary dial, switch-hook, mechanical ringer, network block, and existing jacks. The added electronics mount reversibly inside the case; no original telephone parts need to be drilled, cut, or permanently altered.
The working prototype can be carried and operated away from a fixed telephone connection, making the original desk telephone usable at meetings, demonstrations, or anywhere compatible cellular service is available.
This is a working engineering archive rather than a finished construction release. The hand-wired prototype operates, while the first integrated PCBs are currently awaiting assembly and validation.
The complete point-to-point wiring and component reference is the primary starting point for recreating the proven hand-wired prototype:
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