Optical telegraph and truck: what they have in common

1. Step 1. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.
2. Step 2. Electrical telegraph — has part — Copper wire. Communication lines.
3. Step 3. Copper wire — is part of — Transformer. Windings.
4. Step 4. Transformer — is part of — Defibrillator. Stepping up the voltage.
5. Step 5. Defibrillator — is part of — Ambulance. A defibrillator.
6. Step 6. Ambulance — evolved from — Truck. A special-purpose vehicle.

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