Call sign

In broadcasting and radio communications, a call sign (also known as a call name or call letters—and historically as a call signal—or abbreviated as a call) is a unique identifier for a transmitter station. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even cryptographicallyencoded to disguise a station's identity. The use of call signs as unique identifiers dates to the landline railroadtelegraph system.