Rotary dial and solar panel: what they have in common

1. Step 1. Rotary dial — is part of — Telephone. A dial.
2. Step 2. Telephone — evolved into — Video call. A telephone with a picture.
3. Step 3. Video call — uses — Smartphone camera. A camera.
4. Step 4. Smartphone camera — is part of — Lunokhod. TV cameras.
5. Step 5. Lunokhod — has part — Solar panel. A solar panel.

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