English: The Alexanderson alternator transmitter in the main building at Grimeton Radio Station, near Varberg, Sweden. The Grimeton transmitter was a transatlantic radiotelegraphy station built in 1924 that transmitted telegram traffic to North America in the early 20th century at a frequency of 17.2 kHz with a power of 200 kW. This is the last surviving example of an Alexanderson alternator, a pre-electronic radio transmitter technology used from 1910 to the 1940s.