The 1A3 is a signal diode and features a 1.4 Volt indirectly heated cathode. Normally dry battery valves are directly heated. Such a valve would find applications where the cathode is not taken to ground or where the filaments of other valves are run in series from a higher voltage supply. Two such valves could be used in a discriminator in an FM radio in the 1950s.

The heater wire is a single thread running vertically through the anode cavity.

Seen from the side the anode can be seen as two fins with a central cylindrical cavity for the cathode.

The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 45 mm tall.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	h	a	k	-	-	a	h

 
Absolute Maximum Operating Conditions

Diode	Vh	Ah	Va	mAa
	1.4	0.15	117	0.5

Thanks to Frank Philipse for supplying the above datasheet

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