TM 1-1510-224-10 NOTE The  attitude  display  on  the  EADI  will power  up  to  the  previously  selected attitude source. (5) Heading pushbutton selector switch.  The heading  pushbutton  selector  switch,  placarded   HDG,  is used to select whether gyro-magnetic compass system # 1 or # 2 will supply heading information to the respective EHSI.      Each   depression   of   the   switch   will   cause   the display  on  the  EHSI  to  alternate  between   MAG1   and MAG2, unless the  SLAVE/FREE switch is set to  FREE, then DG1 or DG2 will be displayed. (6) VOR/localizer pushbutton selector switch. The VOR/localizer pushbutton selector switch, placarded V/L, is used to select which  VHF navigation receiver will provide    information    to    the    respective     EFIS.        Each depression of the switch alternates the navigation source display on the EHSI between VOR1 or VOR2, or  ILS1 or ILS2,    depending    upon    whether    a   VOR    or    localizer frequency   has   been   selected   on   the   respective   VHF navigation receiver control panel. The    VOR/localizer    switch    may    be    used    to activate the preview mode on the EHSI if: INS  is  displayed  on  the  EHSI  as  the  navigation source LNAV     flight     director     mode     annunciator     is displayed on the EADI System is powered-up using the primary on-side VHF navigation receiver. The     preview     mode     may     be     cancelled     by depressing the V/L switch. (7) INS/TACAN  pushbutton  selector  switch. The     inertial     navigation     system/TACAN     pushbutton selector  switch,  placarded   INS/TCN,  is  used  to  select whether the  INS or   TACAN  will  provide  information  to the  EFIS.    Each  depression  of  the  switch  will  alternate the navigation source annunciator on the EHSI between INS and TCN. (8) Double-needle    pointer    bearing    source selector   switch.      The   double-needle   pointer   bearing source selector switch, located on the lower right side of the  display  controller,  is  used  to  select  which  navigation information    sources    will    provide    information    to    the double-needle bearing pointer. (a) OFF.        Removes    double-needle pointer from the EHSI. (b) VOR2.      Double-needle   pointer   receives bearing information from # 2 VHF navigation receiver. (c) ADF. Double-needle pointer receives    bearing    information    from    ADF    navigation receiver. (d) INS. Double-needle pointer receives  bearing  information  from  the  inertial  navigation system. (e) TCN. Double-needle pointer receives   bearing   information   from   TACAN   navigation receiver. (9) Weather radar dim control.  Control of the intensity  of  the  weather  radar  display  on  the  EHSI  is accomplished   by   a   control   knob   placarded   WX   DIM, which   is   an   inner   concentric   knob   with   the   HSI   DIM knob. The WX DIM  control  dims  only  the  raster  on  the EHSI  which  contains  the  weather  radar  information.    If the  EHSI  is  in  the  composite  mode  with  the  EADI,  the WX DIM control is used to dim the attitude sphere. (10) EHSI dim control.  Control of the intensity of    the    raster    and    stroke    writing    on    the    EHSI    is accomplished   by   a   control   knob   placarded   HSI   DIM, which   is   an   outer   concentric   knob   with   the   WX   DIM knob.    Turning  the  knob  counterclockwise  to  the   OFF position  will  cause  the  EHSI  to  become  blank  and  the composite mode to be displayed on the EADI. (11) Decision  height  setting  control  and  EFIS test switch. (a) Decision height setting control.  The decision  height  setting  control,  placarded   DH/TEST,  is an   inner   concentric   knob   with   the    ADI    DIM    knob. Rotating the  DH  knob  allows  setting  the  decision  height display  on  the  EADI  in  10-foot  increments  from  200  to 990 feet, and in 5 foot increments from 0 to 200 feet.  By rotating the DH knob completely counterclockwise to the OFF    position,    the    decision    height    display    may    be removed from the EADI. (b) EFIS  test  switch.    Depressing  the EFIS  test  switch,  placarded   TEST,  will  cause  the  EFIS displays  to  enter  a  test  mode.    In  the  test  mode,  flags and cautions are presented along with a test of the radio altimeter.    Observe  the  following  after  depressing  the TEST switch: NOTE A  complete  test  of  the  EFIS  is  only  functional  on  the ground.    Radio  altimeter  test  is  functional  at  all  times except during glideslope CAP/ TRK. Course   select,   heading   select,   DH   set,   DME distance, and   GSPD/TTG  digital  displays  are  replaced by amber dashes. ATT and HDG displays are flagged. 3-24