| Answer | Crossword Clue |
|---|---|
| THORIUM | Element in vacuum tube filaments |
| TRIODE | Three-element vacuum tube |
| ARGON | Gas in a vacuum tube |
| KENOTRON | Vacuum tube used in television. |
| NEON | Light in a vacuum tube. |
| ANODE | ... dark space (region in a vacuum tube) |
| NEON | It glows red in a vacuum tube. |
| ELEMENT | One of the electrodes in a vacuum tube. |
