Letter frequency xz. Modern International Morse code (generally believed to have been developed by Alfred Vail based on English-language letter frequencies of the 1830s) encodes the most frequent letters with the shortest symbols; arranging the Morse alphabet into groups of letters that require equal amounts of time to transmit, and then sorting these groups in increasing order, yields e it san hurdm wgvlfbk opxcz jyq. Similar ideas are used in modern data-compression techniques such as Huffman coding. Letter frequency was used by other telegraph systems, such as the Murray Code. Letter frequencies, like word frequencies, tend to vary, both by writer and
American Morse code US needing to be proficient in both codes since messages on transatlantic cables were in the international code, and incoming messages needed to be recoded and sent on in American Morse. An attempt in 1854 to make International Morse the standard within the US was rejected by the telegraph companies. Overhead wires, used for most land routes in the US, have nowhere near as big a problem with dispersion as undersea or underground cables and the companies had no wish to retrain their staff. In the late 1890s, radio communication—initially known as "wireless telegraphy"—was invented, and used Morse Code transmissions.