Gauge needle and dial and telephone: what they have in common

1. Step 1. Gauge needle and dial — is part of — Hygrometer. It shows the humidity.
2. Step 2. Hygrometer — is part of — Weather station. A hygrometer.
3. Step 3. Weather station — is used in — Weather forecast. Observations.
4. Step 4. Weather forecast — uses — Electrical telegraph. Collecting reports by telegraph.
5. Step 5. Electrical telegraph — evolved into — Telephone. The telephone grew out of attempts to send several signals over telegraph lines (the “harmonic telegraph”).

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