The 18042 is a special quality pentode designed for use in telephone systems. The life quoted is 10,000 hours.

The envelope is clearly marked with the SQ designation.

The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 58 mm tall.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	g2	g1	k	h	h	a	ic	ic	g3,s

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	18	0.1	210	120	-1	10.0	2.1	0.5M	9.0

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 31 August 2008 {find valves by name}