This is the schematic symbol of an old radio tube from the 1940´s. It´s the UBL1 Duodiode-Output Pentode. elektroniska utdata pentod Radio Tube UBL1
This is the schematic symbol of an old radio tube from the 1940´s. It´s the UCH4 Triode-heptode. elektroniska radio röret uch4 trioden Radio röret uch4