The RotaryCell build guide

Convert a rotary phone for cellular service.

Build the electronics, prepare the wiring, load the firmware and install RotaryCell in a Western Electric 500-series telephone.

Start with materials →

A completed RotaryCell conversion

Before you begin

Experience expected

This is not an introductory electronics project. You should be comfortable soldering and desoldering, crimping small contacts, following pinouts and checking your work with a multimeter.

A note on the photos

Several phones, one guide

The photographs were taken across several builds. Shell colors, network blocks, original wiring and routing vary. Follow labels and written connections; use the photos for orientation and clearance. Wire colors only matter where the text assigns them a function.

Build sequence

Follow the project in order from sourcing through the first call. Preparing the LilyGO contains nearly all of the fine soldering and accounts for roughly 80% of the hands-on assembly. The work becomes much more straightforward after that stage.

01Materials and sourcingChoose the parts, order the boards and prepare your tools.→ 02Prepare the LilyGO Most of the hands-on workRemove the original holder and add the battery, audio, power and control connections.→ 03Board assemblyFit the remaining components and inspect your soldering.→ 04Wire harnessesPrepare the cables and verify every connection.→ 05Firmware and SIMLoad the software and establish cellular service.→ 06Install and adjustMount everything, connect the phone and set the audio.→ 07Final checksCheck calling, ringing and battery operation.→

The guide follows the LilyGO controller, Audio/Reset A4 board and AG1171 carrier installed in a Western Electric Model 500 telephone.