Interchangeable parts and optical telegraph: what they have in common

1. Step 1. Interchangeable parts — works like — Movable type. Movable type is an early case of interchangeable parts: identical letters move from line to line.
2. Step 2. Movable type — evolved into — Linotype. Mechanized typesetting.
3. Step 3. Linotype — uses — Tin. A line is cast from type metal (lead, tin, antimony).
4. Step 4. Tin — is material for — Phonograph. The recording is on tin foil.
5. Step 5. Phonograph — was inspired by — Electrical telegraph. Edison came to the phonograph while working on recording telegraph and telephone signals.
6. Step 6. Electrical telegraph — evolved from — Optical telegraph. The electrical telegraph replaced semaphore lines.

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