Tunnel portal e optical telegraph: o que têm em comum

1. Passo 1. Tunnel portal — faz parte de — Tunnel. Tunnel portals.
2. Passo 2. Tunnel — tem como parte — Street light. Lighting.
3. Passo 3. Street light — tem como parte — LED. LEDs.
4. Passo 4. LED — faz parte de — Traffic light. LEDs.
5. Passo 5. Traffic light — evoluiu de — Railway semaphore. The first traffic light was a railway-style semaphore.
6. Passo 6. Railway semaphore — evoluiu de — Optical telegraph. The semaphore idea.

Abrir Evothings