The 101F is a directly heated spherical telephone repeater triode on the GPO bayonet base. The 101F is electrically similar to the 101D (See the STC version 4101D) but the heater requirement has been reduced from 1 Amp to 0.5 Amp.
The enclosed triode construction. The electrodes are supported at the top in a glass bead. The filament tension springs are attached to the support at the extreme left of the image. The grid is formed of shaped wires and the bright anode is spot welded to the side supports.
Side view showing the glass rod supporting the electrodes.
Face view showing the stitches holding the anode plates together.
Oblique view showing the form of the grid winding.
Looking into the top of the anode shows the grid passing flat in front of the anode either side of the filament. The hooks at the ends of the tension springs can just be seen.
The balloon envelope is 58 mm in diameter, and excluding the UV base pins is 94 mm tall.
