A maker known as Thumblegudget built a functional engine-room telegraph for in-home spousal communication, pairing two physical indicator units across different rooms of the house. One unit sits in his office, the other in the living area. When he flips his to 'busy,' the arrow on his wife's unit moves to match. The system works in both directions.
Each unit runs an ESP32-S3, a gimbal motor, and a rotation sensor. The rotation sensor lets the motor snap-lock into discrete positions on the dial when nudged. The two units synchronize wirelessly. A bell, lifted directly from ship telegraph design, alerts the other person that the indicator has changed. No app, no phone, no notification badge.
The full video walkthrough is worth watching for the hardware detail alone: how the gimbal motor is tuned to hold position, how the ESP32 handles sync, and why this form factor works better than a shared screen ever could. The original article is short, but the build video is where the real documentation lives.
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