The PABC80 is a triple diode triode specifically designed for the detector stage in AM/FM receivers. This valve is designed to operate in a 300 mA heater chain directly across the mains. The UABC80 differs only in the heater rating, whereas the EABC80 was designed for the higher anode voltage found in designed with transformer derived HT as well as a 6.3 Volt heater.
Normally this valve featured in a ratio detector circuit for FM demodulation and a diode detector for AM as well as the first stage of audio amplification. SeeFM Broadcasting and Signal Detection.
The three sections are all the same external size. The connections at the top are for the heaters of each section.
The triode is on the left. The outer boxes of the diode sections are screens the anodes are the small vertical elements that can be seen through the holes in the end wall.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 69 mm tall.
References: Data-sheet & 1040. Type PABC80 was first introduced in 1952. See also1952 adverts.