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BELL SYSTEM TECHNICAL JOURNAL 



by modulation and filtration at low power and then its power is 

 built up to a large value in a succession of powerful amplifiers. It 



Fig. 5 



will be appreciated, therefore, that the large-power amplifiers and in 

 particular the water-cooled tubes which are their essential elements 

 represent one of the major problems of the development. 



High-Power Tubes 



The development of the high-power tubes is described quite fully 

 in another paper 4 . The present discussion is, therefore, limited to a 

 few of the outstanding features. 



*Bell System Technical Journal, July 1922 



