When you are at a safe altitude and clear of the immediate departure corridor, the tower will release you to a higher-level air traffic service. This is typically:
Departure Control (or Radar – at larger aerodromes, handles aircraft in the first phase after takeoff
Approach Control – at medium aerodromes, provides approach and departure services
Area Control/Center – at smaller aerodromes or for higher-altitude operations
The controller will instruct you: "Contact Departure/Approach/Radar on frequency [frequency]."
When the controller gives you a new frequency, you must:
Read back the frequency /strong> – Word-for-word and digit-by-digit, exactly as given
Acknowledge – Usually with just "OE-CMV" (or your callsign or "will contact Departure, OE-CMV"
Leave the tower frequency – Once you have read back the frequency, you are clear to switch
Important: Reading back a frequency means you are implicitly acknowledging that you have received it and will contact that service. You do not need to say "leaving frequency" or request permission to leave—the frequency change itself is your clearance to depart.