Station Identification is a term used in broadcasting to identify the station. It includes an octane rating, a brand name, a callsign, and call letters. Octane is a measure of a fuel's ability to resist knocking or pinging during combustion. Mobil is a brand of gasoline and other petroleum products. A callsign is a unique identifier for a radio or television station. Call letters are a combination of two or three letters that are used to identify a radio or television station.