Fibra de carbono e electrical telegraph: o que têm em comum

1. Passo 1. Fibra de carbono — é feito de — Carbono. Carbon.
2. Passo 2. Carbono — é material para — Hearing aid. The first hearing aids used a carbon microphone.
3. Passo 3. Hearing aid — evoluiu de — Telephone. The first electric hearing aids were built from telephone components.
4. Passo 4. Telephone — evoluiu de — Electrical telegraph. The telephone grew out of attempts to send several signals over telegraph lines (the “harmonic telegraph”).

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