Tall wooden churn and internet: what they have in common

1. Step 1. Tall wooden churn — is part of — Butter churn. A tall narrow container.
2. Step 2. Butter churn — uses — Lever. A dasher.
3. Step 3. Lever — is used in — Optical telegraph. The arms were moved by a system of levers and rods.
4. Step 4. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.
5. Step 5. Electrical telegraph — works like — Packet switching. An analogy: telegraph messages were passed from station to station with intermediate storage — a “store and forward” principle similar to packet transmission.
6. Step 6. Packet switching — is used in — Internet. Data is sent in packets.

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