Gauge needle and dial e telephone: o que têm em comum

1. Passo 1. Gauge needle and dial — faz parte de — Hygrometer. It shows the humidity.
2. Passo 2. Hygrometer — faz parte de — Weather station. A hygrometer.
3. Passo 3. Weather station — é utilizado em — Weather forecast. Observations.
4. Passo 4. Weather forecast — utiliza — Electrical telegraph. Collecting reports by telegraph.
5. Passo 5. Electrical telegraph — evoluiu para — Telephone. The telephone grew out of attempts to send several signals over telegraph lines (the “harmonic telegraph”).

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