The DE4 is a rare valve, little used and not generally included in contemporary lists. This exhibit has the type two BBC stamp and dates from between 1924 and 1927, probably around 1925 when this type was introduced. The base pins are of two part construction.
The design purpose was for audio output applications in broadcast receivers.
The base and brass two part base pins.
The Osram logo etched into the envelope.
The BBC stamp and the type designation of DE4 etched into the glass. The filament volts are given as 3.8 Volts.
The elaborate anode fixings with filament top support passing in front of the anode. The BBC stamp has the words Entirely British Manufacture.
Another view of the type designation DE4.
The balloon envelope is 55 mm in diameter and, excluding the B4 base pins, is 106 mm tall.
References: 4051 & 1003 Type DE4 was first introduced in 1924.