Sensibly equivalent¶ to:
The DER stands for Dull Emitter Receiving. It is a general purpose triode with a thoriated tungsten filament, and follows early valve design layout the of a horizontal anode cylinder containing a wire helix grid and a single thin wire filament.
The valve is marked to indicate that the filament voltage is 1.8 to 2.0 Volts at up to 0.4 Amps. Clearly designed for use with a lead acid accumulator for the filament supply. The anode voltage is to be 30 - 80 Volts.
The valve is marked with the BBC stamp and this places this valve to between 1924 and 1927.
The balloon envelope is 48 mm in diameter and, excluding the B4 base pins is 90 mm tall.
Reference: 1003. Type DER was first introduced in 1921.
Absolute Maximum Operating Conditions¶
Updated July 31, 2015.