GPS (satellite navigation) and railway semaphore: what they have in common

1. Step 1. GPS (satellite navigation) — is used in — Car navigator. GPS.
2. Step 2. Car navigator — has part — Liquid-crystal display. A screen.
3. Step 3. Liquid-crystal display — has part — LED. LED backlighting.
4. Step 4. LED — is part of — Traffic light. LEDs.
5. Step 5. Traffic light — evolved from — Railway semaphore. The first traffic light was a railway-style semaphore.

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