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DDT

Sensibly equivalent to:
11A2 A23A AC/HL/DD HD4 MHD4 TDD4
See also:
The Double-Diode Triode
    
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The DDT is a double diode triode for detection and first AF amplifier in superhet receivers. It was introduced in 1933 and the data-sheet makes it clear that it was intended for Automatic Volume Control (now called AGC) and explains how to use the diodes.
The reverse is plain zinc paint.
The classic envelope is 45 mm in diameter and, excluding the B7 base pins, is 106 mm tall.
References: Datasheet & 1043. Type DDT was first introduced in 1933.

 

Pin Connections
B7
1
2
3
4
5
6
7
tc
a(d2)
m
a(d1)
h
h
k
a
g1

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
4.0
1.0
200
-3
3.4
17,000
2.4
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated March 17, 2014.
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