DIFF Subgroup
H03F 3/40 with tubes only
Introduced: September 1968
Full Title
Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements > DC amplifiers with modulator at input and demodulator at output; Modulators or demodulators specially adapted for use in such amplifiers > with tubes only
No child classifications to compare. This is a leaf node in both IPC and CPC.