AT40 (Army Transmitting) balloon Marconi-Osram pip top – AT40X long bulb Marconi Osram helix grid circa 1920s
AT40 Marconi Osram balloon top pip £ 1,000 pair.
AT40X Marconi Osram helix grid horn £ 1,000 pair.
Description
Marconi Osram AT40 balloon valves you see on the left stand for Army Transmitting valve with typical filament of 7 Volts .
The early stage of technology saw most of these valves based on the “R” type, especially the helix grid of the pair AT40X you see on the right with pip/horns. Both pair of valves are dated from 1921 onward.
Tested and working
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