TRACON vs. ARTCC

TRACON, or Terminal Radar Approach  Control, is the air traffic controller which is not commonly known for as they air in a building only looking at radar screens. They typically range from 30-50 miles outside of airport and below 10,000 feet. They are in charge of guiding aircraft to airports and once they are within 5 miles they hand over the aircraft to the air traffic controller in the airport tower. However, before aircraft are handed off to TRACON, ARTCC is in charge of them. ARTCC, or Air Route Traffic Control Center, are in charge of en-route aircraft and are typically divided by two sectors, high-level (above 24,000 feet) and low-level (below 24,000 feet). There are 21 different ARTCC across the United States, each covering a specific area as shown below.

As you can see both controllers must work together to ensure there is no loss in communications with aircraft nor confusion. It is vital that the aircraft copy the correct radio frequency when transferring between sectors or air traffic controllers. The National Airspace System is a complex machine and air controllers are merely the cogs that make it happen.