| Year | 1921 |
| Date | 11-Aug |
| Volume | 45 |
| Issue | 1,059 |
| Page | 119 |
| Category | Radio Engineering |
| Part | |
| Title | The Testing of Thermionic Triodes |
| Author | Captain H. de A.Donisthorpe |
| Notes | Filament current test, backlash test for vacuum, filament emission, "Thermagnion" test for vacuum, amended diagram of wireless circuit |