Prestressed concrete and telephone: what they have in common

1. Step 1. Prestressed concrete — has part — Wire rope. Tensioned tendons.
2. Step 2. Wire rope — uses — Wire drawing. The wire is drawn.
3. Step 3. Wire drawing — is used in — Copper wire. Drawing.
4. Step 4. Copper wire — is part of — Electrical telegraph. Communication lines.
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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