20 Jul
2010
20 Jul
'10
9:23 p.m.
In 1942, the RMA introduced a scheme for
special-purpose and
transmitting tubes, that was called the "1A21" system. ?The first
number represents the power rating, the second, the tube type (e.g.
diode, triode, etc.), the second and third numbers are assigned in
the order of introduction, starting with 21. ?So the gas thyratron
2D21 tells us nothing more than it's a tetrode rated for 10 watts or
less.
That standard lasted only until 1944.
It lived on well past 1944 with diodes and transistors. The 1N4007 is
part of the system as is 1N21.
--
Will