The International Telecommunication Union (ITU) allocates call sign prefixes for radio and television stations of all types. [1 ] They also form the basis for, but may not exactly match, aircraft registration identifiers.
A new generation of cellular standards has appeared approximately every tenth year since 1G systems were introduced in 1979 and the early to mid-1980s.
But in some cases, especially among amateur radio operators other, by ITU unallocated, callsigns are used when operating from disputed areas or countries that are internationally not (yet) recognized.