Like the LS7 (CV1660) the LS7B is a telephone repeater triode. The LS7 has an anode impedance of 5 kΩ - half that of this valve. The LS7 dates to 1929 and this variant must be later.
A a low power valve the anode box is left bright. Construction features electrode supports retained by a side mounted glass rod.
The Marconi label with the glass rod visible above.
The glass rod holding the electrodes and three filament tension springs. The grid is close wound.
The three filament loops can be seen to be oxide coated.
The balloon envelope is 50 mm in diameter and, excluding the B4 base pins, is 96 mm tall.
