Geneva drive and electrical telegraph: what they have in common

1. Step 1. Geneva drive — is part of — Film projector. Intermittent advance of the film.
2. Step 2. Film projector — has part — Lens. A projection lens.
3. Step 3. Lens — is used in — Optical telegraph. Signals were read through telescopes.
4. Step 4. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.

Open Evothings