The DD/207 or DD.207 is a double diode with common filament. It has a very low filament power and can only be designed for signal applications. The DD/207 was introduced by Mazda in 1937 and the metalised paint screening is typical of the period.
The whole of the glass is covered in the zing loaded screening paint.
The classic envelope is 40 mm in diameter, and excluding the B4 base pins is 89 mm tall.
References: Datasheet, 1040 & 1043. Type DD207 was first introduced in 1937.
Absolute Maximum Operating Conditions¶
Updated September 26, 2018. shape:classic construction:pinch type:double.diode age:1930.1940 base:b4 heater:2.0v pins:4 pin:1.a(2) pin:2.a(1) pin:3.f pin:4.f