Crystal Fire #4

Bell Telephone Labs grew around the efforts of American Telephone & Telegraph to develop vacuum tubes for long distance communication. Through a variety of gimmicks, the Bell System enabled transmitting telephone calls over 1000 miles by 1900. Beyond that distance, transmission deteriorated. For transcontinental service to become a reality, the company needed a “repeater” device to replenish the electrical signals at points along the line. AT&T installed a transcontinental line by 1915. Repeaters in Salt Lake City, Omaha, and Pittsburgh boosted the electrical signals.

In the 1920s and 1930s the new discipline of quantum mechanics was used to discover the movement of electrons and the properties of conductors, insulators and semiconductors. New theories superseded older ones. Walter Brattain began work at Bell Labs in 1929. He and colleague Joseph Becker became interested in copper-oxide rectifiers. Copper-oxide belonged to a new class of substances called “semiconductors.” They had some unique properties different from both conductors and insulators. Unlike metals, the conductivity increases with increasing temperature. Copper-oxide rectifiers, dubbed varistors”, began to replace bulky vacuum diodes throughout the Bell system. The speed at which this happened was restrained at Bell Labs by a lack of physicists with enough understanding of quantum mechanics and a hiring freeze during the Great Depression.