Sisal fiber board and telephone: what they have in common

1. Step 1. Sisal fiber board — is part of — Darts. Compressed fibre that holds the darts.
2. Step 2. Darts — is made of — Plant fibre. Modern ones are made of compressed sisal.
3. Step 3. Plant fibre — is material for — Hygrometer. Humidity was shown by a fibre that changed length.
4. Step 4. Hygrometer — has part — Spring. The tension of the hair.
5. Step 5. Spring — is part of — Rotary dial. A return spring.
6. Step 6. Rotary dial — is part of — Telephone. A dial.

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