THE CONTRIBUTORS TO THIS ISSUE 153 



Edward C. Molina, Engineering Department of the American 

 Telephone and Telegraph Company, 11)01-19, as engineering assist- 

 ant; transferred to the Circuits Design Department to work on ma- 

 chine switching systems, 1905; Department of Development and 

 Research, 1919 — . Mr. Molina has been closely associated with 

 the application of the mathematical theory of probabilities to trunking 

 problems and has taken out several important patents relating to 

 machine switching. 



William C. Helmle, B. S., University of Wisconsin, 1917; Uni- 

 versity of Chicago, 1919-20; Commercial Engineer's Ofifice, American 

 Telephone and Telegraph Company 1920 — . 



E. T. HocH, B.S., in Electrical Engineering, Case School of Ap- 

 plied Science, 1914; Western Electric Company, Manufacturing and 

 Installation Departments, 1914-15; Engineering Department, 1915 — . 



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

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

 Wireless Telegraph Company of America assistant engineer, 1909- 

 10; American Telephone and Telegraph Company, Engineering 

 Department and Department of Development and Research, 1910 — . 

 Took part in long distance radio telephone experiments from Wash- 

 ington to Hawaii and Paris, 1915; since then his work has been con- 

 nected with the development of radio and carrier systems. 



J. B. Johnson, B.S., University of North Dakota, 1913; M.S., 

 1914; Ph.D., Yale, 1917; Engineering Department, Western Elec- 

 tric Company, 1917 — . Since coming to the Western Electric Com- 

 pany, Mr. Johnson has devoted much time to high vacua and ioniza- 

 tion in gases. 



