ATC

• ARTCC: Air Route Traffic Control Centers.
  • callsign: center.
  • e.g. Oakland Center.
  • only ~20 ARTCCs in the US.
  • https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/air_traffic_services/artcc
• TRACON: Terminal Radar Approach Control Facilities.
  • callsign: approach, departure.
  • e.g. NorCal Approach.
• actc:Airport Control Tower Communications Read more at http://acronymsandslang.com/meaning-of/airports-and-locations/ACTC.html
• FSS
  • callsign: radio.
  • not controlling traffic.
  • e.g. Oakland Radio, Prescott Radio.

Tower vs ARTCC vs TRACON

Towers handle airport operations, ARTCCs/En-route handle cruise phase, and TRACONs handle climbing and descending aircraft, as well as aircraft transiting between ARTCCs in their controlled areas.

Tower and TRACON

TRACON may be on a separate site or colocate with a tower. For example, California has 5 TRACON, 3 of them colocate with a tower (Santa Barbara, Fresno, Bakersfield) and 2 are independent (Northern California TRACON, near Sacramento; Southern California TRACON, near San Diego).

Clearance Frequency

Clearance Delivery Frequency is initial clearance from ATC before you take off.