TM 1-1510-225-10 3D-24 d.  Airport 4 Page.   The APT 4 page is used to display  communication  frequencies.     Refer  to  Figure 3D-23. (1)   Airport Identifier.  An arrow precedes the identifier if it is the active waypoint. Table 3D-7.  Runway Surface DISPLAY EXPLANATION Blank Blank indicates runway surface unknown. CLY Clay DRT Dirt GRV Gravel HRD Hard surface (includes asphalt, concrete, pavement,  sealed, tarmac, brick, and bitumen) ICE Ice MAT Steel Matting SHL Shale SND Sand SNW Snow TRF Turf KORL ATIS*127.25 CLR *118.05 GRND*121.40 TWR *118.70 CTAF*118.70 APT+4 Figure 3D-23.  APT 4 Page (2)   Frequencies.      Refer   to   Table   3D-8  for frequency abbreviations and their explanations. (3)   In addition to the standard VHF frequencies, HF frequencies are shown at airports that utilize    HF    communications    in    the    2000    kHz    to 30,000 kHz    frequency    band.        Airports    that    have numerous communication frequencies will have multiple APT 4 pages, indicated by APT+4.  Part-time operation is indicated with an asterisk to the left of the frequency.  Refer to Figure 3D-24. (4)   Frequencies associated with CL B, CL C, TRSA,  CTA,  or  TMA  are  VFR  frequencies.    Airports that have one of these categories of frequencies also have    APR    and    DEP    which    are    IFR    frequencies.   Where required, APR, DEP, CL B, CL C, TRSA, CTA, and  TMA  frequencies  are  sectorized.    The  format  for showing   the   sectorization   is   to   show   the   frequency first,    followed    by    the    identifier    of    the    associated reference    point,    followed    next    by    the    applicable radials, and, finally, the associated altitude restrictions. Table 3D-8.  Frequency Abbreviations DISPLAY EXPLANATION AAS Aeronautical Advisory Service AFIS Aerodrome Flight Information Service APR Approach Control ARVL Arrival ATF Aerodrome Traffic Frequency ATIS Automatic Terminal Information Service AWOS Automatic Weather Observing Station CL B Class B (VFR Frequency) CL C Class C (VFR Frequency) CLR Clearance Delivery CTA Control Area (VFR Frequency) CTAF Common Traffic Advisory Frequency CTR Center   (When   Center  Is  Used  For Approach/Departure Control) DEP Departure Control DIR Director (Approach Control/Radar) GRND Ground Control MCOM Multicor MF Mandatory Frequency PCL Pilot controlled lighting PTAX Pre-Taxi Clearance RAMP Ramp/Taxi Control RDO Radio RDR Radar Only Frequency TMA Terminal Area (VFR Frequency) TRSA Terminal  Radar  Service  Area  (VFR Frequency) TWR Tower UNIC Unicom