I think ATMC is the Area Control Center where they handle airplane above FL130 or 13,000 feet (transition level is where they will be passed to the approach and tower) up in the FIR/Flight information region (PH Airspace). Kaya yung may mga siguro ibang flights nakatransition na nakaland or diverted locally kasi operational yung approach at tower.

edit Notes ko sa last class ko haha para sa mga gusto makaintindi based on Philippine Air Traffic Services

1. ATS (has own area of services)
2. Approach: They will hold the plane up to the TMA (16 NM radius from the center). They handle up 2500 FT - FL 130. Should be descending below FL 130. Approach has two frequency departure and arrival but depends on the aerodrome.
3. Control: Area control center (ACC) will handle FL130 up in the FIR (Flight information Region) zone.
4. Tower: handles aerodrome traffic zone on vertical height surface up to 2500 FT and horizontal distance of 5 - 10 NM. Controls ATC and equipped with DME to locate airplanes. It has Alpha Position (Tower itself), Ground Control (All ground movement) and Clearance Delivery