Railway switch and telephone: what they have in common

1. Step 1. Railway switch — is part of — Railway track. Switches.
2. Step 2. Railway track — inspired — Time zones. Introduced because of railway timetables.
3. Step 3. Time zones — uses — Electrical telegraph. Synchronizing time by telegraph.
4. Step 4. 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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