Call letters are a set of unique alphanumeric characters assigned to a radio or television station for identification. They are also known as call signs or station identifiers. The term 'call letters' is commonly used in the broadcasting industry, however, there are several synonyms that can be used interchangeably. Broadcasters may also refer to them as station ID, station call, station branding, or simply call sign. These terms all refer to the same concept of identifying a particular broadcasting station. The use of call letters has been present since the beginning of broadcasting, and it remains an essential aspect of the industry to this day.