Beam tetrode used in the output stage of battery powered radios. Equipped with a centre-tapped filament allowing use in either a parallel filament arrangement running from a 1.5 volt battery or a series arrangement with other 50 mA filaments.
1.4/2.8 V directly heated cathode.
Series filament strings were used in radios designed to be operated from either battery or mains power.
Manufacturer: Radio Corporation of America, USA

Physical Description

Cylindrical glass bulb on octal base with six pins present.

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