Vending machine and hollerith tabulator: what they have in common

1. Step 1. Vending machine — includes — Arcade machine. A coin-operated machine.
2. Step 2. Arcade machine — has part — Cathode-ray tube. A CRT monitor.
3. Step 3. Cathode-ray tube — uses — Electromagnetism. The beam is deflected by a magnetic field.
4. Step 4. Electromagnetism — is used in — Hollerith tabulator. The counters click with electromagnets.

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