Alexanderson alternator
NSS began transmitting in September, 1918 using a pair of Federal Electric 500 kilowatt Poulson Arc transmitters. However, arc transmitters were significantly inferior to the then state-of-the-art Alexanderson alternator and one of the arc transmitters was replaced by a more modern TAW 300 kilowatt vacuum tube transmitter in 1931. VLF, or "longwave" radio was the standard at the time for long range radio transmission, only to be replaced by shortwave in the early 1930s.