Document scanner bar and hollerith tabulator: what they have in common

1. Step 1. Document scanner bar — is part of — Fax. It reads the sheet line by line.
2. Step 2. Fax — uses — Telephone. Transmission over a telephone line.
3. Step 3. Telephone — uses — Telephone exchange. Connecting subscribers.
4. Step 4. Telephone exchange — has part — Relay. Relay switching.
5. Step 5. Relay — is part of — Hollerith tabulator. Relays controlled the sorting box.

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