Maritime call sign

These mimicked an earlier railroad telegraph convention where short, two-letter identifiers served as Morse code abbreviations to denote the various individual stations on the line (for instance, AX could represent Halifax).

[2] Later that same year, an international conference standardised radio call signs so that the first two letters would uniquely identify a transmitter's country of origin.

In the case of states such as Liberia or Panama, which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters (for example, 3LXY, and sometimes followed by a number, i.e. 3LXY2).

As broadcast stations became commonplace in the 1920s, some original three- and four-letter call signs were reassigned as the corresponding ships were removed from U.S. registry.

Similarly, WEZU, the international radio call sign of the ship SS Lash Atlantico, was assigned in 1997 to a broadcast station.