The Contributors to this Issue 



George A. Campbell, B.S., Massachusetts Institute of Technology, 

 1891; A.B., Harvard, 1892; Ph.D., 1901; Gottingen, Vienna and 

 Paris, 1893-96. Mechanical Department, American Bell Telephone 

 Company, 1897; Engineering Department, American Telephone and 

 Telegraph Company, 1903-1919; Department of Development and 

 Research, 1919 — ; Research Engineer, 1908 — . Dr. Campbell has 

 published papers on loading and the theory of electric circuits and is 

 also well-known to telephone engineers for his contributions to re- 

 peater and substation circuits. The electric filter which is one of his 

 inventions plays a fundamental role in telephone repeater, carrier 

 current and radio systems. 



Robert W. King, A.B., Cornell University, 1912; Ph.D., 1915; 

 assistant and instructor in physics, Cornell, 1913-17; Engineering 

 Department of the Western Electric Company, 1917-20; Depart- 

 ment of Development and Research, American Telephone and Tele- 

 graph Company, 1920-21; Information Department, 1921 — . While 

 with the Western Electric Company, Mr. King's work related to the 

 design and construction of vacuum tubes and allied high vacuum 

 apparatus. 



Karl K. Darrow, S.B., University of Chicago, 1911; University 

 of Paris, 1911-12; University of Berlin, 1912; Ph.D., in physics and 

 mathematics, University of Chicago, 1917; Engineering Department, 

 Western Electric Company, 1917 — . At the Western Electric, Mr. 

 Darrow has been engaged largely in preparing studies and analyses 

 of published research in various fields of physics. 



H. D. Arnold, Ph.B., Wesleyan, 1906; M.S., 1907; Ph.D., Chicago, 

 1911; assistant in physics, Wesleyan, 1906-07; Chicago, 1908; pro- 

 fessor, Mt. Allison, 1909-10; Engineering Department of the Western 

 Electric Company, Research Engineer, 1911 — ; Director of Research, 

 1923 — . Dr. Arnold has been in direct charge of the development 

 of the vacuum tube for telephone repeaters and radio purposes, and 

 also other items of telephone equipment. 



Lloyd Espenchied, Pratt Institute, 1909; United Wireless Tele- 

 graph Company as radio operator, summers, 1907-08; Telefunken 

 Wireless Telegraph Company of America, assistant engineer, 1909-10; 



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