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ID = 31422
Great Britain (UK)
Brand: Osram-Valves GB (not MO-Valves)
Tube type:  Electrometer Triode   Text 
  Late but very rare. ***
Identical to ET1

Base Europe 4-Pin B4 (Eu A, E, 4A) 1914 Top contact screw type.
Was used by Technology / Measurement
Filament Vf 1 Volts / If 0.1 Ampere / Direct / Battery =

Electrometer triode for high impedance measurements. The grid is connected on top of the high glass stem, not the anode!
Also Marconi.
0.05 mA/V Gm at 4V anode and -2V grid, rises to 0.1 mA/V at +6V anode and -2V grid. Grid current in the order of 10exp-16 A.
A comprehensive article on this very special vacuum tube and its application was given in these pages from Wireless World, November 26th 1936.

The tube was developed in 1930.

Text in other languages (may differ)
Information source - - Manufacturers Literature   
ET1: Private collection
Emilio Ciardiello

Emilio Ciardiello

ET1: Manufacturer's Literature
Emilio Ciardiello

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