TM 1-1510-225-10 3D-39 five dots left and right of the center position, each dot represents one nautical mile of deviation. NOTE In some installations where the KLN 90B is interfaced     to     certain     models     of     EFIS equipment,    the    scale    factor    will    be    ± 7.5 nautical miles, full scale. (2)   The    course    is    defined    by    the    active waypoint and the selected magnetic course.  A course to or from the waypoint may be selected. (3)   The course selection is normally made by changing the selected cours e displayed on an external indicator such as an EHSI or EFIS.  When this is done, the  pilot  must  verify  that  the  proper  course  has  been selected   by   confirming   the   digital   selected   course readout displayed on the KLN 90B.  In the OBS mode, the selected course is always displayed as part of the mode annunciation at the bottom center of the screen on all pages except the Super NAV 5 page.  Refer to Figure   3D-53.        On    the    Super    NAV    5    page,    the mode/annunciation is displayed on the left side of the screen.      Two   or   more   navigation   sources   can   be selected  as  the  primary  navigation  source  displayed on  the  EHSI  or  EFIS.    The  primary  navaid  selector switch  on  the  pilot's  side  of  the  instrument  panel  is used  to  determine  the  navigation  source  displayed.   For   the   KLN   90B    to    properly    read    the    external indicator,    the    KLN    90B    must    be    the    displayed navigation source on the external indicator. Figure 3D-53.  OBS Mode Indications (4)   When  the  KLN  90B  is  not  the  displayed navigation  source  on  the  external  indicator  or  if  the KLN   90B   is   interfaced  with  an  EFIS  system,  it  is possible  to  change  the  selected  course  from  several pages  on  the  KLN  90B.    This  can  be  done  from  the NAV 3 page, the MOD 2 page, and the Super NAV 5 page if it is configured to display the track on the left- hand side. NOTE To  tell  if  it  is  possible  to  enter  the  OBS value, note the OBS field. If a colon follows the  letters  OBS,  it  is  possible  to  enter  a value.    If  the  colon  is  missing,  the  course must be changed from the external indicator. If  the  KLN  90B  is  interfaced  to  EFIS  or an electrically    driven    mechanical    indicator, the   external   indicator   will   be   slewed   to agree  with  what  was  entered  on  the  KLN 90B. 1.     Select  the  NAV  3,  MOD  2  or  Super NAV 5 page. 2.     Press  the  appropriate    CRSR  button to  turn  on  the  cursor  function.    If  the course    is    being    changed    from    the Super NAV 5 page, use the left outer knob   to   rotate   the   cursor   over   the OBS field. 3.     Turn  the  appropriate  inner  knob  to select the course. 4.     Press the CRSR button to turn off the cursor function. (5)   There is no automatic leg sequencing   or turn anticipation. (6)   The minimum ESA displayed on the NAV 3  page  is  the  highest  MSA  sector  altitude  from  the present    position    to    the    active    waypoint.        Other waypoints  in  the  active  flight  plan  do  not  affect  the ESA. (7)   When  the  active  waypoint  is  a  VOR  or approach  waypoint,  the  published  magnetic  variation for  the  VOR  or  approach  waypoint  is  utilized  rather than the calculated magnetic variation. d.  Switching From the LEG Mode to the OBS Mode.    The  following  mode  transition  occurs  if  the KLN 90B is in the LEG mode and the mode is changed to OBS. (1)   The   waypoint   that   was   active   in   LEG mode  prior  to  the  mode  change  remains  the  active waypoint in OBS mode. (2)   The  selected  course  is  defined  by  two different  methods  depending  on  the  installation  and status of the unit. (a)   If   the   KLN   90B   is   the   displayed navigation  source  when  the  change  is  made  to  the