The R19 is a directly heated EHT rectifier for television service. The anode voltage quoted is the peak inverse voltage and this is important in a television EHT generator as the waveform is pulsed and not a sine wave.This exhibit is an import and carries the ugly word Foreign. (Subtext - buy British).
The R12 has a higher specification than the 1X2B and can be used as a direct substitute for the 1X2B.
The bell anode has an extra support in the shape of a mica ring.
The helical coated filament.
The filament is seen here behind the rod that forms the top connection. The mica ring around the anode is of double thickness. This raises the possibility that it was suitable for use in areas of shock and vibration - military?
Another view of the filament.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 65 mm tall.
