What is the function of a "departure frequency"?

The function of a departure frequency is specifically designed to facilitate communication between air traffic control and aircraft that are in the process of taking off and climbing out after departure. This frequency is crucial for ensuring safe and efficient handling of the aircraft as they leave the ground and begin their ascent.

When a pilot contacts the departure frequency, air traffic controllers provide instructions for initial separation from other departing and arriving aircraft, helping to establish a safe and manageable airspace environment. This communication typically includes altitude assignments, routing instructions, and any other pertinent information necessary for the aircraft to transition safely from the airport's controlled environment into the en route phase of their flight.

In contrast, options related to landing procedures, emergency communications, or general air traffic control communication do not accurately reflect the specialized role played by a departure frequency in managing departures specifically. Therefore, the focus on initial separation after takeoff marks why this choice is the correct definition of a departure frequency.