f | Filament connection. Directly heated cathode. |
h | Heater connection. |
hct | Heater centre tap connection. |
k | Cathode. Source of electrons. Normally at ground potential. |
g1 | Control grid. Nearest grid to cathode. Normally held negative of cathode. |
g2 | Screen grid. Normally connected to external positive voltage. |
g3 | Suppressor grid. Normally connected to cathode. |
g4 etc | Additional grids used in specialist valves such as frequency changers. |
a | Anode. Normally connected to a high positive voltage. |
bp | Beam forming plates. In beam tetrodes to focus the electrons. |
() | Used to indicate the electrode set where several exist in the envelope. |
s | Internal screen to shield the electrodes. |
ic | Internal connection. Nothing must be connected to this pin of the valveholder. |
tc | Top cap connection. Normally the anode(s) are taken to top caps. |
m | Metalising internal or external to the valve. |
