“International Telecommunication Union (ITU) An international organization established to standardize and regulate international radio and telecommunications. The ITU allocates call sign prefixes for radio and television stations of all types. These prefixes are agreed upon internationally and are a form of country code. A call sign can be any number of letters and numerals, but each country must only use call signs that begin with the characters allocated for use in that country. The call signs may be viewed on a chart or a grid.”