Summary

Although classified as a tetrode because it has two grids, this valve is not a screen grid type. It is a 'space-charge' valve where the inner grid is connected to a small positive voltage and the outer grid is used as the control grid. This allowed operation on very low plate voltages. 3.5 volt directly heated cathode.
As a detector this valve will work satisfactorily with a plate voltage between 2 and 4 volts, as an amplifier, it requires 4 to 10 volts.
Philips used Roman numbers in the type numbers of their first commercial receiving valves so this valve is in fact a D6.
Manufactured by: Philips, Holland

Physical Description

Spherical bulb with exhaust tip on top. 4 pin European style base with side terminal.

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