This water-cooled microphone was invented by Charles "Doc" Herrold. Although first developed and used in 1913, it was patented in 1915 by Herrold and Emil Porter, one of his students. In 1909, Herrold was the first to broadcast radio entertainment and information for an audience on a regularly scheduled, pre-announced basis. Along with his broadcasts as 6XL, or "San José Calling," Herrold operated his College of Wireless and Engineering from the Garden City Bank building in San José, California. He was forced off the air in 1917 by a wartime ban on non-governmental radio broadcasting. In 1921, he received a license as KQW in San José. In 1949 KQW became KCBS, San Francisco. The Perham Collection includes extensive documentation regarding the work of Doc Herrold, and his early relationship with National Radio and many of California's early radio technicians and broadcasters.