The Louden PER1 is a four volt battery audio output triode. The PER1 also came in a six Volt version. The details are found on the paper strip wrapped round the base moulding.
The filament is a single strand that passes through two concentric wire helix's. The inner being the control grid and the outer the anode.
The filament has burnt out and all electrodes are held in folds and clamped supports. Usually tungsten wire is clamped but nickel and molybdenum is spot welded.
The left end of the electrodes.
The balloon envelope is 47 mm in diameter, and excluding the B4 base pins is 88 mm tall.
References: 1043. Type PER1 was first introduced in 1926. See also1926 adverts.
