Intercom and conveyor belt: what they have in common

1. Step 1. Intercom — has part — Microphone. A microphone.
2. Step 2. Microphone — has part — Diaphragm. The diaphragm vibrates under a sound wave.
3. Step 3. Diaphragm — is part of — Drum. A diaphragm.
4. Step 4. Drum — is made of — Leather. The drumhead is stretched hide.
5. Step 5. Leather — is material for — Conveyor belt. The first belts were leather.

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