The BTH (British Thomson-Huston Co) B5 is a triode that was released in 1923. It is designated as a general purpose valve and has an amplification factor (μ) of 7. The low filament current is indicative of a dull emitter valve. The filament rating of 2.8 Volts was chosen so that the valve could be heated by two dry cells in series.
The BBC stamp is a variant of the second stamp to be used by participating companies. This dates our exhibit to between September 1924 and 1927. The wording reads 'Made in England' and the official wording was 'Entirely British Made'. See also B5 and B5.
The balloon envelope is 37 mm in diameter and, excluding the B4 base pins, is 88 mm tall.
Reference: 1003. Type B5 was first introduced in 1923.
Absolute Maximum Operating Conditions¶
Updated May 17, 2015.