Thyristor and needle: what they have in common

1. Step 1. Thyristor — evolved from — Diode. A controllable counterpart of the diode with a four-layer structure.
2. Step 2. Diode — evolved from — Vacuum tube. The first diode was a vacuum tube (Fleming); later diodes became semiconductor devices.
3. Step 3. Vacuum tube — includes — Iconoscope. An electron tube.
4. Step 4. Iconoscope — is made of — Silver. The target is a mosaic of silver grains with caesium.
5. Step 5. Silver — is material for — Syringe. Early needles were silver.
6. Step 6. Syringe — has part — Needle. A hollow needle.

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