TM 1-1510-225-10 3A-1 CHAPTER 3A AVIONICS  R Section I.  GENERAL 3A-1.  INTRODUCTION. This    chapter    covers    all    avionics    equipment installed  in  the  C -12  R   aircraft.    It  provides  a  brief description of the equipment, the technical characteristics,  and  locations.    It  covers  systems  and controls   and    provides    the    proper    techniques    and procedures  for  operating  the  equipment.    For  more detailed   operational   information,   consult   the   vendor manuals that accompany the aircraft loose tools. 3A-2.  AVIONICS EQUIPMENT CONFIGURATION. The aircraft's avionics consist of three groups of electronic    equipment.        The    communication    group consists  of  the  intercom  system,  AM/FM  (VHF/UHF) transceiver, two VHF-AM transceivers, HF transceiver, an    Emergency    Locator    Transmitter    (ELT),    and    a cockpit voice recorder.  The navigation group consists of two VOR/localizer/glideslope/marker beacon receivers,  Automatic  Direction  Finder  (ADF)  receiver, TACAN  receiver,  a  multi-sensor navigation system, a radio    altimeter    system,    a    gyromagnetic    compass system, an Electronic Flight Instrument System (EFIS), and   a   digital   integrated   flight   control   system.      The transponder  and  radar  group  consists  of  a  weather radar  system,  transponder,  and  a  servoed  encoding altimeter indicator.  The transponder and radar group includes   an   identification,   position,   and   emergency tracking    system,    and    a    radar    system    to    locate potentially    dangerous    weather    areas.        A    Ground Proximity  Altitude  Advisory  System  (GPAAS)  is  also installed. 3A-3.  POWER SOURCE. a.   DC   Power.        DC    power    for    the    avionics equipment  is  provided  from  four  sources:  the  aircraft battery,  left  and  right  generators,  and  external  power.   Power    is    routed    through    two    50-ampere    circuit breakers    to    the    avionics    power    relay,    which    is controlled  by  the   AVIONICS  MASTER  PWR  switch located on the pilot's subpanel, Figure 2-5.    Individual system  circuit  breakers  are  shown  in  Figure  2-6 and the  associated  avionics  buses  are  shown  in  Figure 2-27, Sheet 1 and Table 2-7. b.  AVIONICS MASTER PWR Switch.  A switch, placarded AVIONICS MASTER PWR OFF, located on the   pilot's   subpanel,   controls  power  to  the  avionics buses. (1)   OFF.    In  the   OFF  position,  power  from the    5-amp    circuit    breaker,    placarded     AVIONICS  MASTER, located on the right sidewall circuit breaker panel,    Figure    2-6,    energizes    the    avionics    relay, removing power from the avionics buses. (2)   On.    With  the  switch  in  the  on  position, the avionics power relay is de-energized and power is applied to the avionics buses. NOTE If the AVIONICS MASTER PWR switch fails to operate, provide power to the individual avionics   circuit   breakers   by   pulling   the 5-ampere circuit breaker, placarded AVIONICS   MASTER,   located   on   the   right sidewall circuit breaker panel. c.   Single-Phase AC Power.          Two     static inverters   supply   400   Hz   single-phase   115   volt   and 26 Vac  electrical  power  to  the  avionics  equipment.   The  inverters  are  controlled  by  a  switch,  placarded INVERTER, NO 1 / OFF / NO 2, located on the pilot's subpanel. Section II.  COMMUNICATIONS 3A-4.  COMMUNICATIONS EQUIPMENT GROUP DESCRIPTION. The  communications  equipment  group  consists of   an   intercom   system   connected   to   a   dual   audio control  panel  serving  both  the  pilot  and  copilot,  which interfaces  with  VHF,  UHF,  and  HF  transceivers  and provides    reception    of    audio    from    VOR,    localizer, marker beacon, TACAN/DME, and ADF receivers. 3A-5.  MICROPHONES, SWITCHES, AND JACKS. Boom   and   oxygen   mask   microphones   can   be used in the aircraft. a.   Control Wheel Microphone Switches.   The pilot  and  copilot  are  each  provided  with  control  wheel microphone switches, placarded   MIC,  located  behind the    outboard    handgrip    of    their    respective    control