The DE4 is a rare valve, little used and not generally included in contemporary lists. Some collectors even doubt that the DE4 existed, but we know of at least three. See DE4 for more information.
We believe that this sample dates from 1925, based on the style of markings and the base. Earlier versions had a metal shell base cap.
This triode is rated at 3.8 Volts filament voltage. This suggests accumulator supplies of 4 Volts nominal. The base is British four pin and the valve is marked with the BBC stamp.
The balloon envelope is 59 mm in diameter and, excluding the B4 base pins, is 105 mm tall.
References: 4051 & 1003 Type DE4 was first introduced in 1924.
PDF scanned from an original document held by the museum
Updated April 06, 2012.