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LT1

 
See also:
DER Valves - The Dawn of Broadcasting in the UK
    
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The LT1 was the first thoriated tungsten dull emitter valve produced in the UK. It was introduced in 1921 and in 1922 it became the DER with a balloon envelope rather than the tube used for the LT1'
This exhibit has the type one BBC Stamp that was introduced in 1922 with the commencement of broadcasting in the UK and so this is clearly one of the last of the LT1 to be made.
In the table below the LT1 is at the top with the DER below.
Thanks to Joe Gruber for sending the images.
The wide glass tube envelope is  mm in diameter and, excluding the B4 base pins, is  mm tall.
Reference: 1003. Type LT1 was first introduced in 1921.

 

Pin Connections
B4
1
2
3
4
a
g1
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
1.8
0.4
36-50

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
μ
1.8
0.35
30-80
-3.0
-
32,000
0.28
9.0
Updated July 16, 2021.
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