Grounding rod and hollerith tabulator: what they have in common

1. Step 1. Grounding rod — is part of — Lightning rod. Electrodes in the ground.
2. Step 2. Lightning rod — uses — Electrical conduction. It carries the current into the ground.
3. Step 3. Electrical conduction — is used in — Track circuit. The wheelset closes the circuit.
4. Step 4. Track circuit — has part — Relay. Track relays.
5. Step 5. Relay — is part of — Hollerith tabulator. Relays controlled the sorting box.

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