TM 1-1510-225-10 3A-29 (10)   Range Down Switch.  Pressing the range down switch, placarded RNG, will select the next lower range  to  be  displayed  on  the  EHSI  while  in  the  NAV MAP    or    WEATHER    modes.        Once    the    lowest selectable range is reached, the range up switch must be used to change range. (11)   Primary Navigation Sensor System Push- Button    Selector    Switch.        The    primary    navigation sensor system push-button selector switch, placarded 1   –   2,   is   used   to   select   either   primary   navigation sensor   system   #1   or   #2   for   display   on   the   EFIS system.        The    primary    NAV    system    selected    is annunciated   as   sensor   1   or   2   on   the   EHSI.      For example,  if  VOR  1  is  being  displayed  and  the   1  –  2 switch  is  pressed,  VOR  2  will  become  the  displayed sensor.  If only one sensor is installed, the display will not cycle and the sensor annunciation will not show a system  number.    For  example,  ADF  is  displayed  (not ADF 1), since only one ADF is installed. (12)   HSI     Double     Needle     Bearing     Pointer Source   Push-Button   Selector   Switch.    Pressing  the HSI   double   needle   bearing   pointer   source   selector switch  selects  the  next  available  sensor  for  display.   The   bearing   pointer   sensor   list   contains   only   those sensors  that  have  bearing  information  capabilities.    If the  selected  sensor  has  distance  information  paired with  it,  that  distance  will  also  be  displayed  below  the sensor annunciation.  Possible sensors for the double needle bearing pointer are as follows. 1.   DECLUTTER    (no    number    one    or number two bearing pointer information is displayed). 2.   VOR. 3.   TCN. 4.   LNAV (GPS). 5.   ADF. 6.   DME number one (distance only). (13)   HSI Single Needle Bearing Pointer Source   Push-Button   Selector   Switch.      Pressing  the HSI   single   needle   bearing   pointer   source   selector switch  selects  the  next  available  sensor  for  display.   The   bearing   pointer   sensor   list   contains   only   those sensors  that  have  bearing  information  capabilities.    If the  selected  sensor  has  distance  information  paired with  it,  that  distance  will  also  be  displayed  below  the sensor  annunciation.    Possible  sensors  for  the   single needle bearing pointer are the same as for the double needle bearing pointer. (14)   HSI Course Select Knob.   Rotation of the course select knob, placarded CRS, allows the course pointer   and   digital   course   to   be   set   to   the   desired course.  Pulling the course  select  knob  out  will  cause the  course  pointer  and  digital  course  readout  on  the EHSI  to  change  to  the  direct  course  to  the  selected navaid or active waypoint. 3A-20.  ELECTRONIC ATTITUDE DIRECTOR INDICATOR (EADI). a.   Description.    The  EADI  combines  a  sphere- type attitude display with lateral and vertical computed steering   signals   to   provide   commands   required   to intercept  and  maintain  a  desired  flight  path.    Refer  to Figure  3A-11  for  EADI  Fault  Annunciators  and  3A-12 for  EADI  Category  II  Symbology.    The  EADI  provides  the following display information. 1.   Attitude display. 2.   Flight director command cue. 3.   Flight director mode annunciations. 4.   Heading. 5.   Vertical deviation. 6.   Expanded localizer. 7.   Radio altitude with rising runway display. 8.   Decision height setting and annunciations. 9.   Marker beacon annunciations. 10.    Air data command. 11.    Rate of turn. 12.    Reversionary annunciations. 13.    Flags. 14.    Comparison monitors.