Eimac Klystron Vacuum Tube, circa 1958

The klystrom is a vacuum tube that amplifies high-range radio frequencies; it is an essential factor in the history of radar, microwave, and telecommunications. Klystroms also power UHF television, particle accelerators, and radiation therapy equipment. In 1937, brothers Russell and Sigurd Varian invented the klystrom, and founded Varian Associates -- one of the first technology companies in Silicon Valley.