Otoscope and hollerith tabulator: what they have in common

1. Step 1. Otoscope — has part — LED. Illumination.
2. Step 2. LED — is part of — Traffic light. LEDs.
3. Step 3. Traffic light — has part — Relay. Relay controllers.
4. Step 4. Relay — is part of — Hollerith tabulator. Relays controlled the sorting box.

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