When is the frequency or frequencies assigned to local control or air traffic control tower used?

The frequency assigned to local control or air traffic control tower is primarily used when an aircraft enters an airport's jurisdiction. This is crucial for managing the safe movement of aircraft within the airport's airspace and on the ground.

When an aircraft approaches an airport, it must communicate with the local control tower to receive instructions regarding landing, taxiing, or any other operational procedures while it is within the passenger terminal's airspace. This communication ensures that the tower can coordinate the various aircraft movements, maintain safe distances between them, and manage any potential conflicts.

Using the frequency when an aircraft enters the airport's jurisdiction establishes a clear communication channel necessary for maintaining order and safety in a busy environment where multiple aircraft might be interacting simultaneously.