Alkaline battery and conveyor belt: what they have in common

1. Step 1. Alkaline battery — is part of — Electronic calculator. A calculator runs on a battery, sometimes on a tiny solar panel.
2. Step 2. Electronic calculator — evolved from — Arithmometer. Electronics replaced mechanics.
3. Step 3. Arithmometer — has part — Crank. The handle for adding and subtracting.
4. Step 4. Crank — is part of — Spinning wheel. A foot drive through a crank.
5. Step 5. Spinning wheel — has part — Belt drive. The wheel is linked to the spindle by a cord.
6. Step 6. Belt drive — is used in — Conveyor belt. The belt runs around the drive and tension drums.

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