AEG Coolidge Therapy Tube

Early Coolidge Therapy Tube, 32” (80 cms) long, dating probably to the late 2^nd decade, 20^thCentury, bearing the AEG mark, Type II, No.3007, and the inscription “Fürstenau Coolidge Röhre, Veifa Werke, Frankfurt A/M”.

Note the flat concentric spiral filament of the “hot cathode” in its molybdenum cylinder, and the round tungsten target embedded in the lightweight copper anode.

The brownish violet discoloration often seen after long use in tubes of this type is due to the potassium impurities in the glass.

       Before the U.S.A. entered WW1, AEG had obtained the privilege of manufacturing Coolidge tubes, and they had them made by Veifa. But the patent for using tungsten anodes belonged to Siemens & Halske. So an agreement was concluded in which each partner granted the other the use of both patents, and in which AEG reserved to itself the right to manufacture certain definite quantities of tubes for Siemens & Halske.

              Georg Siemens:”History of the House of Siemens”, 1957, Karl Alber, Vol II, p.80)

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