TM 1-1510-224-10 Heading selection Glideslope deviation Time-to-go Heading and navigation source annunciators Heading synchronization (2) Partial compass displays. Weather radar Lightning sensor system data Navigation map b. EHSI Controls, Indicators, and Functions (fig.  3- 13). (1) Course/desired track display.  The course (CRS)/desired  track   (DTRK)   display   provides   a   digital digital   readout   of   the   course   selected   by   the   course pointer (yellow) or the desired track when navigation with information   supplied   by   the   INS.      Course    (CRS)    or desired track  (DTRK)  are  displayed  in  white  letters  with the numerical course displayed in yellow. (2) Single-needle     bearing     pointer.          The single-needle  bearing  pointer  (blue  circle)  indicates  the relative  bearing  to  the  selected  navaid.    The  navigation source  is  indicated  by  the  single-needle  pointer  source annunciator.        When    the    bearing    pointer    navigation source   is   invalid   or   a   localizer   frequency   has   been chosen,   the   bearing   pointer   will   be   removed   from   the display. (3) Heading source annunciator. The heading source annunciator will display  MAG1 or  MAG2 when slaved or  DG1 or   DG2  when  free,  to  show  which gyrocompass system is providing heading information to the EHSI. (4) Heading    marker.        The    notched    blue heading  marker  is  positioned  on  the  heading  dial  by  the respective    heading    selection    knob    on    the    remote instrument   controller   panel,   which   is   located   on   the pedestal  extension  (fig.    2-14).    Once  set  to  the  desired heading, the heading marker will maintain its position on the  heading  dial.    The  difference  between  the  heading marker   and   the   lubber   line   index   is   the   amount   of heading    select    error    applied    to    the    flight    director computer.      In   heading   mode,   the   EADI   pitch   and   roll command cue will display the proper bank commands to turn  to  and  maintain  this  selected  heading.    Pulling  on the heading select knob (pedestal extension, fig. 2-14) will set the heading marker to aircraft heading. (5) Lubber line.  Aircraft heading is read from the heading dial under the lubber line. (6) Double-needle    bearing    pointer.        The double-needle bearing pointer (green diamond) indicates the    relative    bearing    to    the    selected    navaid.        The navigation   source   is   indicated   by   the   double-needle pointer  source  annunciator.    When  the  bearing  pointer navigation  source  is  invalid  or  a  localizer  frequency  has been  chosen,  the  bearing  pointer  will  be  removed  from the display. (7) DME hold annunciator.  Illumination of the amber DME hold (H) annunciator indicates that hold has been  selected  on  the  VOR  navigation  receiver  control panel   that   is   supplying   navigation   information   to   the respective EHSI. (8) Navigation    source     annunciator.        The navigation   source   that   is   being   used   by   the   EHSI   is indicated   by   the   illumination   of   a   navigation   source annunciator.  Possible annunciations are   VOR1,  VOR2, ILS1,  ILS2,  TCN, and   INS.    All  the  annunciations  are white,  except  INS  which  is  annunciated  in  blue  to  show that it is a long range navigation system.  The navigation source   will   annunciate   amber   if   the   pilot   and   copilot select   the   same   navigation   source.      The   navigation source  will  annunciate  amber  if  the  pilot  has  selected VOR2 or if the copilot has selected VOR1. (9) Distance  display.    The  distance  display indicates  the  distance  in  nautical  miles  to  the  selected DME    station    or    INS    waypoint.        When    short    range navigation  information  is  being  used  the  distance  will  be displayed  in  a  0  to  399.9  nautical  mile  format.    When long  range  navigation  (INS)  information  is  being  used the distance will be displayed in a 0 to 3999 nautical mile format. DME    distance    is    supplied    to    the    EFIS    by channels # 1 and # 2 of the three channel TACAN/DME unit.    Channel  #  I  provides  the  TACAN  distance  data when  TACAN  is  the  selected  navigation  source  or  DME distance   data   when   NAV1   is   the   selected   navigation source.  Channel # 2 provides distance data when  NAV2 is the selected navigation source. (10) Previ ew  course  pointer  navigation  source annunciator.      The   preview   course   pointer   navigation source  annunciator  displays  which  navigation  source  is being used by the preview course pointer. (11) Glideslope deviation pointer, annunciator, and   scale.      The   glideslope   deviation   pointer   shows aircraft deviation from the center of the glideslope beam. The  G  annunciator  on  the  glideslope  deviation  pointer indicates     that     the     information     being     presented     is glideslope  deviation.    Deviation  from  the  center  of  the glideslope  beam  is  measured  by  the  glideslope  scale. The distance between two dots is equal to a 0.35 degree deviation.    The  glideslope  display  will  not  be  present  on the EHSI unless a valid ILS frequency has been tuned. 3-32