The Cossor New Process 220HPT is a battery audio output pentode.

The top view shows the wire grids within the bright anode cavity.

The load resistance is 10,000 ohms and this is greater than high impedance headphones, so clearly this valve would have been used with an output transformer to transform the impedance to that required by a loudspeaker.

The balloon envelope is 43 mm in diameter and, excluding the B5 base pins, is 90 mm tall.

 
Pin Connections

B5	1	2	3	4	5
	a	f-	g1	f+	g2

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm	Pout	D
	2.0	0.2	150	150	-4.5	8.0	1.5	2.5	0.5W	8%

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 09 June 2007 {find valves by name}