The 240QP is a directly heated double pentode for quiescent push-pull audio output stage use in battery receivers. It was designed to operate from an accumulator filament supply and a 120 Volt HT battery. The two pentodes being designed to operate in class B1 with a drive of 19 Volts pk-pk across the grids.
The pair of pentode sections. As a low power device the anodes are left bright.
The pinch and the mass of connections. The three wire grids can be seen above the bottom mica that holds the pentode section together.
Seen from the base the flat inter-connections between the separate pentode sections can be clearly seen. Within the anode the shape of the wire grids can also be seen. The oxide coated filament can be seen to consist of four vertical strands.
The B7 base with compression pins and the evacuation tube seen within the base.
The classic envelope is 45 mm in diameter and, excluding the B7 base pins, is 103 mm tall.
References: Data-sheet & 1043. Type 240QP was first introduced in 1936. See also1936 adverts.