From The New York Times Book of Essential Knowledge
St. Martin’s Press, NY, 2004. Technology, p. 445
Desch and Mumma’s Electronic Accumulator
The next major leap in computing technology involved the use of vacuum tubes as on/off valves. This enabled calculations to be made electronically rather than mechanically, which resulted in a significant increase in calculating speed.
The first use of the vacuum tube in a computing device was in 1938, when Joseph Desch (1907-1987) and Robert Mumma (1905-) built a machine they called the Electronic Accumulator. This machine primed the world for the true first-generation computers, and would be the dominant switching technology for the next 20 years.