Placed in Service". At the same time extensive advances were being made in radio transmitter design, with the new equipment employing vacuum-tube technology. Since Herrold had been refining now outdated arc-based systems, much of his technical knowledge was becoming obsolete. Radio development post-World War One Effective October 1, 1919, the wartime ban on civilian radio stations was lifted. Herrold renewed his two expired licenses, 6XE for portable operations in the fall of 1920, and 6XF, a standard Experimental license, in the spring of 1921. There were still no formal requirements for stations wishing to broadcast entertainment to the general public, and pioneer broadcasting activities, now using vacuum-tube equipment, were being started independently at scattered sites. One of Herrold's first tasks after the end of the war was to become familiar with vacuum-tube equipment. Although some of his associates later thought that he resumed regular broadcasts as early as 1919, there is no record of him returning to the airwaves prior to early May 1921, presumably over 6XF, when an announcement was made that his school would begin programs on Monday and Thursday nights, playing records supplied by "J. A. Kerwin of 84 East Santa Clara street, dealer in phonographs". Broadcasting station KQW (later KCBS) The government eventually adopted a regulation, which took effect on December 1, 1921, requiring that persons wanting to transmit entertainment to the general public had to obtain a Limited Commercial license. Thus, on December 9, 1921, a license with the randomly assigned call sign of KQW was issued in the name of Charles D. Herrold in San Jose. Operation of the broadcasting station was financed by sales of radio equipment by the Herrold Radio Laboratory, but by 1925 the costs for KQW had grown burdensome, and the station was transferred to the First Baptist Church of San Jose. Two conditions of the reassignment were that Herrold be kept on as program director, and the station's sign-ons include the statement: "This is KQW, pioneer broadcasting station of the world, founded by Dr. Charles D. Herrold in San Jose in 1909". However, at the end of 1926 Herrold's contract with the station which he had founded would not be renewed. A few months later he started working for station KTAB in Oakland, California, primarily in sales. Herrold did not profit financially from his pioneering work, and later became a repair technician in the Oakland, California school district, and