Measures for Progress: A History of the National Bureau of Standards

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452 THE NEW WORLD OF SCIENCE (1946-51)
The four stages of an early printed electronic circuit: the plate, the circuit wiring, addition
of the resistors, and final assembly with miniature tubes.
for measuring the characteristics of the growing family of electron tubes to
determine, among other things, the principles by which their life service might
be extended.72 A new field of research was the semiconductors, crystalline
materials of high purity, such as germanium and silicon. With their elec-
trical conductivity between that of a metal and an insulator, and their unique
ability to change their resistance characteristics, they opened new vistas in
the development of communication equipment.73 They appeared first in the
crystal diode developed during the war for radar, and subsequently in the
crystal triode or transistor, as replacements for the vacuum tubes in amplifiers.
The ubiquitous pocket transistor radio was less than a decade away.
New advances were made in printed circuits. first devised for the
proximity fuze, that substitute printed wiring, resistors, and coils for the
conventional rigging in electronic devices. Along with subminiature tubes,
semiconductors, and circuit design, the printed circuit established a whole
72 NBS Annual Report 1948, p. 244; Annual Report 1949, p. 80.
72 NBS Annual Report 1949, P. 21; Annual Report 1951, p. 4.