Call Sign

An assigned sequence of letters or letters and figures used to identify a radio station or vessel in communications.

For ships, the call sign is normally assigned by the responsible national administration from international call-sign series allocated under ITU arrangements. It is used in voice and digital radio services to identify the station unambiguously.

A call sign is distinct from the vessel’s name, Maritime Mobile Service Identity and IMO ship identification number, although systems such as AIS may display several of them together. Prefixes can indicate an allocation series, but should not be interpreted using a few example first letters alone.