The PM4DX triode design dates from 1929. The envelope has etched into it a 4DX and also the Mullard logo that appeared on the ORA of an aerial-coil-and earth symbol. Additionally the envelope carries a code D208.

The balloon envelope is 43 mm in diameter and, excluding the B4 base pins, is 90 mm tall.

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	4.0	0.1	150	-4.5	3.5	7,500	2.0

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This exhibit was last updated on 02 December 2007