Thermal print head and bicycle: what they have in common

1. Step 1. Thermal print head — is part of — Fax. It prints the received image.
2. Step 2. Fax — uses — Photodiode. Scanning with a photocell.
3. Step 3. Photodiode — is part of — Pulse oximeter. A photodiode.
4. Step 4. Pulse oximeter — has part — LED. Red and infrared LEDs.
5. Step 5. LED — is part of — Bike light with dynamo. An LED.
6. Step 6. Bike light with dynamo — is part of — Bicycle. A lamp.

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