Lock and key and hollerith tabulator: what they have in common

1. Step 1. Lock and key — evolved into — Smart lock. An electronic lock.
2. Step 2. Smart lock — has part — Servomotor. A bolt actuator.
3. Step 3. Servomotor — uses — Electromagnetism. A servo is an electric motor with feedback.
4. Step 4. Electromagnetism — is used in — Hollerith tabulator. The counters click with electromagnets.

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