TM 1-1510-225-10 3B-1 CHAPTER 3B AVIONICS  T3 Section I.  GENERAL 3B-1.  INTRODUCTION. This    chapter    covers    all    avionics    equipment installed  in  the  C-12  T3  aircraft  and  provides  a  brief description of the equipment, the technical characteristics, and locations.  If the item is common to all three aircraft, C-12R, C-12T3, and C-12F3, you will be referred to the appropriate paragraph in Chapter 3.   For more detailed operational information, consult the vendor   manuals   that   accompany   the   aircraft   loose tools. 3B-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   (V/UHF) SATCOM  transceiver,  two  VHF-AM  transceivers,  HF transceiver   OSA , an Emergency Locator Transmitter (ELT),  and  a  cockpit  voice  and  data  recorder    OSA  .   The navigation group consists of two VOR/localizer/glideslope/marker beacon receivers, Automatic  Direction  Finder  (ADF)  receiver,  Distance Measuring     Equipment     (DME),     Global     Positioning Systems   (GPS)   FMS   1-FMS-800   and    FMS 2-KLN 90B,    radio    altimeter,    Electronic    Flight    Instrument System    (EFIS),    Automatic    Flight    Control    System (AFCS),  and  a  gyromagnetic  compass  system.    The transponder  and  radar  group  consists  of  a  weather radar  system,  transponder,  Traffic  Alert  and  Collision Avoidance System (TCAS), Lightning Detection System (Stormscope), and a Ground Collision Avoidance System (GCAS). 3B-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 2-28 and Table 2-8. (1)   Avionics  Master  Power  Switch.  A switch placarded AVIONICS MASTER PWR OFF, located on the   pilot's   subpanel,   controls   power   to   the   avionics buses. (a)  Off.    In  the  aft  (off)  position,  power from the 5 -ampere 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. (b)  On.    With  the  switch  in  the  UP  (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. (2)   DC   Auxiliary   Bus.      DC   power   may   be applied to an independent bus for isolated operation of the  UHF  and  COMM  1  radios,  pilot’s  audio  system, and instrument indirect lights.  Use of the auxiliary bus is  independent  of  the  battery  master  switch  position, but  is  controlled  by  a  two  position   ON  /  OFF switch, placarded  DC  AUX  BUS, located under the gang bar with the battery and generator switches.  Placing this switch in the  ON  position  will  provi de battery power to the    auxiliary    bus    for    operation    of    the    previously mentioned  equipment  should  an  electrical  emergency such as a dual bus failure occur in-flight, or if operation of    the    equipment    is    desired    during    pre/postflight operations. b.  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.