Rotor from Fessenden Rotary Spark Gap, Used at the Naval Wireless Station NAA, Arlington, Virginia, 1913

This device was part of a system used to amplify the time signal from U.S. Navy station NAA at Arlington, Virginia. Station NAA received a time signal from the Naval Observatory clock via telegraph wire, rebroadcasting it via a powerful transmitter to receivers all over the nation. Americans utilized radio technology to set their clocks to this standardized signal.