The UBC81 small double diode triode was probably used for signal demodulation and AGC detection in universal mains domestic equipment. The triode section could be used for a first stage of amplification after the detection process.

The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 52 mm tall.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	a	g1	k	h	h	a(d1)	s	a(d2)	ic

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	gm	μ
	14	0.1	250	-1.5	5.0	1.65	70

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 01 February 2008 {find valves by name}