Industrial Revolution and radio: what they have in common

1. Step 1. Industrial Revolution — uses — Coal. Coal.
2. Step 2. Coal — is a kind of — Carbon. Mostly carbon.
3. Step 3. Carbon — is material for — Hearing aid. The first hearing aids used a carbon microphone.
4. Step 4. Hearing aid — has part — Amplifier. An amplifier.
5. Step 5. Amplifier — is part of — Radio. Amplifying a weak signal.

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