Leibniz’s stepped reckoner and railway semaphore: what they have in common

1. Step 1. Leibniz’s stepped reckoner — evolved into — Arithmometer. Thomas’s arithmometer used Leibniz’s stepped drum.
2. Step 2. Arithmometer — evolved into — Electronic calculator. Electronics replaced mechanics.
3. Step 3. Electronic calculator — has part — Liquid-crystal display. An LCD display.
4. Step 4. Liquid-crystal display — has part — LED. LED backlighting.
5. Step 5. LED — is part of — Traffic light. LEDs.
6. Step 6. Traffic light — evolved from — Railway semaphore. The first traffic light was a railway-style semaphore.

Open Evothings