One of the provisions of the Radio Act of 1912 was that, in a limited number of cases where it was shown to be of value, amateurs could be issued "Special Amateur" licenses, that permitted operation in the band of wavelengths from 600 to 200 meters (500 to 1500 kHz). Maxim successfully convinced government regulators that relay work fell into this category, and in the spring of 1915 Tuska was upgraded to a Special Amateur license, with the call sign 1ZT, which permitted operation on the standard relay wavelength of 425 meters (706 kHz)."Special Land Stations", Radio Service Bulletin, May 1915, page 4. The "Z" in 1ZT's call sign reflected the fact that the station was operating under a Special Amateur license.
