Pager and dewar flask: what they have in common

1. Step 1. Pager — has part — Liquid-crystal display. The message appears on an LCD.
2. Step 2. Liquid-crystal display — is part of — Monitor. Then LCDs.
3. Step 3. Monitor — has part — Cathode-ray tube. The first monitors were CRTs.
4. Step 4. Cathode-ray tube — uses — Vacuum. Inside is a vacuum.
5. Step 5. Vacuum — is used in — Dewar flask. A vacuum.

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