DX
DX was a common telegraphic abbreviation that stood for a signal that travelled a very long distance. It is still used today in the field of radio, but is most frequently used in amateur radio circles.
DX is also a system of document exchange, used widely by British lawyers as a a fast and reliable alternative to the postal system. A DX address will read something like DX 12345 Nottingham.
See also: TX and RX
