The Contributors to this Issue 



Otto J. Zobel, A.B., Ripon College, 1909; A.M., Wisconsin, 1910; 

 Ph.D., 1914; Instructor in physics, 1910-15; instructor in physics, 

 Minnesota, 1915-16; Engineering Department, American Telephone 

 and Telegraph Company, 1916-19; Department of Development and 

 Research, 1919 — . Mr. Zobel has made important contributions to 

 circuit theory in branches other than the subject of wave-filters. 



J. N. Kirk, B.S., Purdue University, 1905; Engineering Depart- 

 ment, New York Telephone Company, 1905-11; Plant Engineer for 

 Texas, Southwestern Bell Telephone Company, 1912; Outside Plant 

 Engineer, 1913-16; Engineering Department, American Telephone 

 and Telegraph Company, 1917-19; Outside Plant Engineer, Depart- 

 ment of Operation and Engineering, 1920 — . 



A. B. Clark, B.E.E., University of Michigan, 1911; American 

 Telephone and Telegraph Company, Engineering Department, 1911- 

 19; Depaitment of Development and Research, 1919 — . Mr. Clark's 

 work has been connected with toll telephone and telegraph systems. 



George A. Campbell, B.S., Massachusetts Institute of Tech- 

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

 and Paris, 1893-96; Mechanical Department, American Bell Tele- 

 phone Company, 1897; Engineering Department, American Tele- 

 phone and Telegraph Company, 1903-19; Department of De- 

 velopment and Research, 1919 — ; Research Engineer, 1908 — -. Dr. 

 Campbell has published papers on loading and the theory of elec- 

 tric circuits, including electric wave-filters, and is also well known 

 to telephone engineers for his contributions to repeater and substa- 

 tion circuits. 



J. E. Harris, A.B., University of Michigan, 1908; M.S., 1909; 

 Ph.D., 1911; instructor in general and physical chemistry, 1911-17; 

 Engineering Department, Western Electric Company, 1917 — . Mr. 

 Harris has been connected with the development of the oxide coated 

 filament used in the manufacture of vacuum tubes. 



E. E. Schumacher, A.B., University of Michigan, 1918; assistant 

 in chemistry, 1917-18; Engineering Department, Western Electric 

 Company, 1918 — -. Mr. Schumacher is engaged in chemical work 

 connected with the oxide coated filament used in the manufacture of 

 vacuum tubes. 



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