Carved stone cylinder and electrical telegraph: what they have in common

1. Step 1. Carved stone cylinder — is part of — Cylinder seal. A stone with a carved image.
2. Step 2. Cylinder seal — works like — Gutenberg printing press. An analogy: both a seal and a press reproduce a pre-carved pattern.
3. Step 3. Gutenberg printing press — uses — Paper. The impression is made on paper.
4. Step 4. Paper — is material for — Loudspeaker. The cone is paper.
5. Step 5. Loudspeaker — is part of — Telephone. The earpiece reproduces the other person’s voice.
6. Step 6. Telephone — evolved from — Electrical telegraph. The telephone grew out of attempts to send several signals over telegraph lines (the “harmonic telegraph”).

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