Rare-earth metals e railway semaphore: o que têm em comum

1. Passo 1. Rare-earth metals — é material para — Smartphone. The magnets of the speakers and vibration motor are rare-earth.
2. Passo 2. Smartphone — tem como parte — LED. The camera flash.
3. Passo 3. LED — faz parte de — Traffic light. LEDs.
4. Passo 4. Traffic light — evoluiu de — Railway semaphore. The first traffic light was a railway-style semaphore.

Abrir Evothings