This valve is a Marconi DE3 triode from 1924.
The filament is rated at 2.8 Volts at 0.06 Amps, this suggests two dry cells in series as the filament supply, but in fact a 4.5 Volt 'bell' battery would be used with a series rheostat. The filament could thus be maintained at the 'correct' voltage. The valve can be used at LF or HF or as a detector according to the label.
The DE3 was designed for use as a detector or AF amplifier.
The construction is a vertical anode 18 mm long and 5 mm diameter, into which the grid and filament fit coaxially. The filament is a single strand, and the grid is a fine wire helix supported on a side rod through the whole length of the anode.
The wide glass tube envelope is 25 mm in diameter and, excluding the B4 base pins, is 91 mm tall.
References: 4051 & 1003 Type DE3 was first introduced in 1924.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated August 10, 2015. shape:wide.glass.tube construction:pinch type:triode age:1920.1930 base:b4 pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f