Carbon rods and bell: what they have in common

1. Step 1. Carbon rods — is part of — Arc lamp. An arc burns between them.
2. Step 2. Arc lamp — is part of — Street light. The first electric street lights were arc lamps (the “Yablochkov candle”, 1878).
3. Step 3. Street light — has part — LED. LEDs.
4. Step 4. LED — is part of — Smartphone. The camera flash.
5. Step 5. Smartphone — evolved from — Alarm clock. The alarm clock moved into the phone.
6. Step 6. Alarm clock — has part — Bell. A bell rings.

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