The 3A5 miniature double triode is for dry battery operation. Uses would be in radio receivers and other portable equipment.

The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.

Reference: Datasheet. Type 3A5 was first introduced^¶ in 1942.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	f-	a(2)	g1(2)	fct	g1(1)	a(1)	f+

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	1.4	0.22	90	-2.5	3.7	8,300	1.8

Thanks to Frank Philipse for supplying the above PDF datasheet

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