The CV1653 is the UK government designation for the STC 3A/108A telephone repeater triode. The design dates from 1947.

The classic envelope is 45 mm in diameter, and excluding the American 4-pin bayonet base pins is 103 mm tall.

Reference: Datasheet. Type CV1653 was first introduced^¶ in 1947.

 
Pin Connections

	1	2	3	4
	g1	f-	f+	a

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm	μ
	2.0	0.2	160	-1.5	-	50,000	0.6	30

Thanks to Frank Philipse for supplying the above PDF datasheet