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A Call Sign is a unique alphanumeric identity assigned to a transmitting radio station. It may contain from 3 up to 7 characters. All stations open to international public correspondence, all amateur stations, and other stations which are capable of causing harmful interference beyond the boundaries of the territory or geographical area in which they are located, shall have call signs.
Assignment of call sign is made by the telecommunication administration concerned. Individual call signs are assigned using the call sign series allocated by the ITU to the administration. These call sign series are contained in the Table of International Call Sign Series (Appendix 42 to the Radio Regulations) and at:http://www.itu.int/online/mms/glad/cga_callsign.sh?lang=enCall sings are formed as indicated in RR19.51 to RR19.71. Call sign formation possibilities for different type of stations can be found at:http://www.itu.int/en/ITU-R/terrestrial/fmd/Documents/fxm-callsignformation.pdf
According to RR19.31 it is not compulsory to assign call signs to stations, which are already identified by maritime mobile service identities or which are easily identified by other means (see RR19.16) and whose signals of identification or characteristics of emission are published in international documents.
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