| Answer | Crossword Clue |
|---|---|
| NEON | Element in vacuum tubes |
| ANODES | Positive poles in vacuum tubes. |
| NEON | Inert gas in vacuum tubes |
| ARGON | Inert gas used in vacuum tubes |
| THORIUM | Element in vacuum tube filaments |
| ARGON | Element in radio tubes |
| YTTRIUM | Element used in old television tubes |
