TM 1-1510-225-10 3B-175 d.  Normal Operation. (1)   Function  Selection.     Position  the  power and mode switch to ANT, ADF, or TONE. (2)   Frequency Selection. Using the preceding frequency select procedures, tune the ADF until  the  desired  frequency  is  indicated  in  the  active frequency display and verify the station identifier. (a)   ANT   Function.      Position  the  power and  mode  switch  to   ANT.    The  RMI  pointer  will  park horizontally.    Select    ADF  on  the  audio  system  and adjust the volume. (b)   ADF   Function.    Position  the  power and   mode   switch   to    ADF.      The   RMI   pointer   will indicate relative bearing to the turned station. NOTE When  the  ADF  system  is  not  receiving  a reliable signal, the RMI pointer will remain parked  in  the  ADF  mode.    The  ADF  may momentarily park during station crossings because   of   signal   loss.      If   the   bearing pointer  fails  to  respond  as  indicated   or ID is lost in ANT position, the ADF should be considered unreliable and will not be used for navigation or approaches.  (c)   TONE  Function.    Position  the  power and   mode   switch   to    TONE.      A   1000-Hz  tone  will identify keyed CW stations. e.   Self-Test. NOTE If   the   si gnal  received  is  weak  or  of  poor quality, the bearing pointer rotation will be slow. 1.   Position   the   power   and   mode   switch   to ADF    and    tune    a    nearby    NDB,    outer marker, or broadcast station and press the TEST  button.    The  RMI  pointer  will  rotate 90° from the previous valid indication. 2.   Release the   TEST  button  and  verify  that the  RMI  pointer  returns  to  that  indication.   Select   ANT   on   the   ADF   control   panel.   Bearing  pointer  should  point  horizontally, and   a   valid   aural   navaid   identifier   (ID) should continue. 3.   Select   ADF   on   the   control   panel.      The bearing pointer should return to the proper relative bearing. 3B-25.  GLOBAL POSITIONING S YSTEM (KLN 90B). Refer to Chapter 3D for detailed information. 3B-26.  FMS 1 DATA LOADER. A  Data  Loader  for  the  FMS  1  is  located  on  the lower  pedestal.    A  Data  Loading  Cartridge  is  used  to load  flight  plans,  save  flight  data,  and  provide  access to  ICAO  identifier.    Refer  to  Paragraph  3B-19u  for  a detailed description of the Data Loader Operations. 3B-27.  ALTITUDE SELECT CONTROLLER. a.   Description.    The  Altitude  Select Controller, located in the center of the instrument panel, provides a  means  for  setting  the  desired  altitude  reference  for altitude alerting and altitude pre-select system.  Refer to Figure 3B-139. b.  Altitude   Alert.      As   the   aircraft   reaches   a point  1000  feet  from  the  selected  altitude,  a  signal  is generated  to  light  the  warning  light  on  the  altimeter and  sound  a  warning  horn  for  1  second.    This  light remains  on  until  the  aircraft  is  300  ±  50  feet  or  more from the selected altitude, the light is again energized and  the  horn  is  sounded.    The  light  remains  on  until the  aircraft  returns  to  within  300  ±  50  feet  or  deviates more than 1000 feet from the selected altitude. c.   Altitude Pre-select.  The altitude is selected by  turning  the  selector  knob  until  the  altitude  display reads  the  desired  value.    No  further  actin  is  taken  on the    controller.        To    initiate    altitude    pre-select,    the ALTSEL    button    is    selected    on    the    flight    director controller.    The  pilot  must  initiate  a  maneuver  to  fly toward the pre-selected  altitude.  Any of the following pitch   modes   may   be   engage:   Pitch   Hold,   Airspeed Hold,   or   Vertical   Speed   Hold.      Upon   initiation   of altitude    pre-select   capture,   the   previously   selected pitch mode is automatically reset. Figure 3B-139.  Altitude Select Controller