BC - Base sleeve            G - Grid                   IS - Internal shield     B - Bean unit
BS - Base shell             H - Heater                  K - Cathode             D - Diode unit
ES - External shield       HL - Heater tap for lamp    NC - No connection      HP - Heptode unit
 F - Filament              HM - Heater mid-tap          P - Plate (anode)      HX - Hexode unit
FM - Filament mid-tap      HS - Heater shield           S - Shell               P - Pentode unit
FT - Fluorescent target    IC - Internal connection    TA - Target              T - Triode unit
                                (do not use)            U - Unit               TR - Tetrode unit