The 20D1 is a double signal diode. Possible uses would be demodulation of signal and AGC voltages. The 200 mA heater requirement suggests universal mains sets.

The two additional pictures show other views of the electrodes. The anodes are mainly flat with a very small circular cavity between the plates for the heater.

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

 
Pin Connections

B7G	1	2	3	4	5	6	7
	k(1)	a(2)	h	h	k(2)	s	a(1)

 
Absolute Maximum Operating Conditions

Diode	Vh	Ah	Va	mAa
	9.5	0.2	175	9

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}