AR

Ra = 36.0 kOhm, slope = 0.17 mA/V, amplification factor = 6.0
. First made in 1922. For several months in 1923 the tube was available with the "Ediswan Safety Cap". The purpose of this base was to stop accidental connection of the filament pins to that of the plate or anode hole in the tube socket. The bases were only the British B4 designation and had three pin lengths. plate/anode and grid pins 18 mm, one filament pin 14.5 mm and the other 12 mm. No other tube manufacturer used these bases and it was not long before they were discontinued by the company. These bases were only used on receiving tubes.

From 1913, the Ediswan company was permitted to use the word "Royal" on lamps (light bulbs) and the this was by Decree from the British Royal Family.The word also appeared on at least four other Ediswan tubes made between 1918 and 1922. (exact dates not known). According to John Stokes, in his book "70 years of radio tubes and valves", page 190, the word was discontinued during 1922.It is assumed that the word "Royal" on radio tubes was not authorised in the first place. Tubes known to have used the word are AR, C, ES4 (2) and R

AR: Fin Stewart Fin Stewart	Just Qvigstad	AR: own collection Peter den Boer

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