Eitel-McCullough operated a large manufacturing plant in San Bruno for many years. William Eitel and Jack McCullogh formed the company in 1934. It specialized in the manufacture of power grid tubes. Known as Eimac, the company also made vacuum tubes used in communication equipment, as well as other products for military and commercial applications. Due to its work on broadcast transmission parts, Eimac operated an FM radio station, KSBR, which transmitted on 100.5 megahertz. The station began operations in 1947 and, that same year, was one of only two in the nation to test Rangertone tape recorders. (The other station was WASH-FM in Washington, D.C.) The recorders were based on the German Magnetophon. In need of more space, the company moved to San Carlos in 1959. Eimac's San Carlos plant was dedicated on April 16, 1959. In 1965, Eimac merged with Varian Associates and became known as the Eimac Division. In 1995, Leonard Green & Partners purchased the entire Electron Devices Business from Varian and formed Communications & Power Industries.