This magnificent example of the R Type was made in England and is branded Marconi's W T Co. The envelope is made of slightly smoked glass and the pin formation suggests that this dates from WW1. See also R Type.![](../pics/aaj0016a.jpg)
The side view above shows the concentric formation of the electrodes and the single fine strand of tungsten that is the filament.![](../pics/aaj0016c.jpg)
The fragile and brittle filament has been partly protected by the coil formation adjacent to the support. This gives a measure of tension to prevent sag when the filament is at operating temperatute. The grid support can also clearly be seen.![](../pics/aaj0016d.jpg)
By processing the photograph to add false colours the lettering becomes visible.The spherical envelope is 52 mm in diameter and, excluding the B4 base pins, is 95 mm tall.References: Private communication, 1005 & 1003. Type R Type was first introduced in 1916. See also 1916 adverts. |