Maschinensender
After Fessenden left NESCO, Ernst Alexanderson continued to work on alternator-transmitter development at General Electric, mostly for long range radiotelegraph use. He eventually developed the high-powered Alexanderson alternator, capable of transmitting across the Atlantic, and by 1916 the Fessenden-Alexanderson alternator was more reliable for transoceanic communication than the spark transmitters which were originally used to provide this service. Also, after 1920 radio broadcasting became widespread, and although the stations used vacuum-tube transmitters rather than alternator-transmitters (which vacuum-tubes made obsolete), they employed the same continuous-wave AM signals that Fessenden had introduced in 1906.