On initial contact with each aircraft, always state your facility identification. On subsequent communications, the facility identification may be omitted.
Each position has a radio callsign. Most callsigns begin with the city name of the airport (Las Vegas for example) followed by a position. For example:
Some facilities will have a name other than the city, which will be given on the approach charts. For example, San Diego Airport uses the callsign “Lindbergh,” and Southern California TRACON uses the callsign “Socal Approach.”
{Reference: FAAO 7110.65 2-4-8 & 2-4-19}