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3.5 × 3.5 × 12.3 cm

This was the first commercial English Tetrode. It has a two-ended structure to keep down inter-electrode capacitance and consequent unwanted feedback between input and output circuits. The tetrode has a screen grid between control grid and anode. This reduces the capacitance between control grid and anode by a factor of nearly 100, thus reducing the Miller Effect, and permits the valve to work at frequencies well above the broadcast band. The tetrode also has a higher gain compared with a similar triode, by a factor of 50 or more.