Ediswan AR bright emitter triode
Ediswan AR 1922/3
1924 prices
This is a bright emitter tungsten filament advanced version
of the 'R' valve, on a nickel plated brass base. Made
between November 1922 and October 1923 by Edison-Swan, this valve
has a 'pip' top where it was pumped during manufacture. The official
type approval BBC stamp, showing that the valve was approved and
that duty had been paid, is clearly visible. This valve was still
on sale in 1924, as you can see by the price list at the left.
Its price of 12/6d is the equivalent of over £100 today in earnings terms.
However the dull emitter, thoriated tungsten filament,
ARDE and AR06 valves, with their very
much reduced current demands, were already replacing it.
Accumulator life between charges was extended at least tenfold
by the newer valves much lower filament power which was as low
as 150 mW compared to the 4 W dissipated by the 'AR' type. They
could even be operated from the more portable dry cell LeClanche batteries.