Call signs in South America are used for a variety of purposes, including identifying radio and TV stations.
Call signs are regulated internationally by the ITU as well as nationally by the Comisión Nacional de Comunicaciones of the Argentine government.
[4] Since 2000 or earlier, call signs beginning with LR and a third letter, as well as have been assigned, For instance, LRL 421 is Canal 21 in Buenos Aires.
in Ciudad Autonoma de Buenos Aires, and LOL Observatorio Naval (National Observatory, a time signal station which operates in Shortwave.
For more information the page Indicativo de chamada (in Portuguese) has a complete description of Brazilian call signs.