“Victor” Early Coolidge Tube







               Early type Coolidge hot cathode tube. 20” (50cms) long. 6” (15cms) strongly discoloured bulb. Bearing a patent number dating to 1918-1919.

               Made by the Victor Corporation, Ohio, USA, bearing the inscription  Broad Coolidge Tube and the text This tube is not licensed to be re-exhausted or repaired. Metal therein licensed to be used exclusively in this tube”.

                  Small tungsten target embedded in a light-weight copper anode.

                  The hot cathode is a slightly convex concentric spiral tungsten filament in a molybdenum cylinder. Edison crew-type external filament connection.


               William D. Coolidge (1875-1973) applied for a patent for this tube on May 9, 1913. The patent was granted on Oct.31, 1916. In his application, Coolidge states :


“……As a cathode I ordinarily use a tungsten filament, and this may be conveniently heated by current from a storage battery, or transformer with suitable regulating devices so that the temperature of the cathode or filament may be adjusted at will. I have found that electrons will be emitted from such a cathode, which electrons will traverse the space between the cathode and the target under the influence of the  electromotive  force impressed  upon  the  tube,  and  by  bombardment of  the  target  will  give  rise  to x-rays……..”




          The introduction of the “Hot Cathode” opened a new era in the practice of radiology. It obviated the instability and the “ temperamental”  behavior of gas discharge tubes of the different types used until then. 

        When asked about the behavior of gas discharge tubes, Röntgen would have stated in a letter “I do not want to get involved in anything that has to do with the properties of tubes, for these things are even more capricious and unpredictable than women”.


          Alongside German researchers like Lilienfeld and Rosenthal, as well as a German patent in the name of Fürstenau, W.D.Coolidge and his assistant Irving Langmuir, perfected a tube in 1913 in the laboratories of the General Electric Co., Schenectady, which soon became known the world over as the Coolidge Tube.

(Georg Siemens “History of the House of Siemens”, Karl Alber, 1957, Vol II, p.79)


About the Victor Electric Corporation


1895 :  “Victor Electric Company” incorporated.   Got involved in 1896 in the manufacture of therapeutic 

                     and x-ray machines.

1916:   Victor, Snook, Macalaster-Wiggin, and Scheidel-Western, combine to form Victor Electric


1920 :  General Electric acquires interest in Victor which reincorporates as “Victor X-Ray Corporation”.

1926 :  “Victor X-ray Corporation” becomes a wholly-owned affiliate of General Electric.

1930 :  “Victor X-Ray Corporation” becomes “General Electric X-Ray Corporation”.

                                                                                  “The Story of X-Ray”, General Electric Co., 1963, p.60

  Go to Category Index
Go to Main Page