The ARDE from Ediswan was introduced in 1923 as a general purpose valve. The ARDE stands for Amateur Radio Dull Emitter and was advertised as a low temperature valve. Ediswan made three versions of the ARDE. The general purpose without additional paint stripes. The red line for RF and Detector use and the green line for Detector and AF use. These three versions also existed in the earlier AR bright emitter valve.
The electrode assembly is mounted vertically and very much the same design as the bright emitter AR valve. The other dull emitter from Ediswan introduced in 1923 the AR.06 also has vertical electrodes and a 3 Volt 70 mA filament.
The underside of the valve. The anode and grid pins are labelled and the filament pins are shorter and of unequal length. This was the Ediswan safely cap.
Before the era of valve data books the specifications of the valve came printed on the box.
Here the side of the box explains the Ediswan safety cap (base). The early valve holders were either moulded with the metal contacts extending to the top of the moulding or were of the spring connector held on an outer ring of ceramic type. The top picture shows the latter type holding this exhibit. A consequence of this open connector arrangement was that if a valve was inserted into its base with the supplies switched on, the filament could be shorted out on the HT supply. The Ediswan safety cap prevented this by having the grid and anode on long pins and the filament on shorter pins. The filament could only make a circuit if the first three pins were inserted in the correct places.
A general view of the box. Inside a square inner box shell contains the valve wrapped in course hair matting. The top and bottom of the valve are protected by cardboard and a square of matting. This is quality packaging.
The cylindrical anode is mounted vertically above the pinch. The helical grid is just under half the diameter of the anode. The filament was a single fine strand of thoriated tungsten wire passing centrally through the grid and held at the top by a spring tension wire.
The wide glass tube envelope is 29 mm in diameter, and excluding the B4 base pins is 92 mm tall.
References: Data-sheet, 1004 & 1003. Type ARDE was first introduced in 1923. See also1923 adverts.