TM 55-1510-222-10 b.  VOL control - As required. 9.  Shutdown procedure: a. VOL/OFF control Turn counterclockwise. 3-24.  ADF RECEIVER (ADF-60). a.    Introduction.    The  ADF  receiver  (FIG.  3-16) provides   aural   reception   of   signals   from   a   selected ground   station   and   indicates   relative   bearing   to   that station.        The    ground    station    must    be    within    the frequency  range  of  190.0  to  1749.5  kHz.    The  ADF receiver has three functional modes of operation.  In the antenna (ANT) mode the ADF receiver functions as an aural  receiver,  providing  only  an  aural  output  of  the received  signal.    In  automatic  direction  finder  (ADF) mode,   it   functions   as   an   automatic   direction   finder receiver   in   which   relative   bearing   to   the   station   is presented  on  an  associated  bearing  indicator,  and  an aural  output  of  the  received  signal  is  provided.    The tone  (TONE)  mode  provides  a  1000-Hz  aural  output tone  when  a  signal  is  being  received  to  identify  keyed continuous  wave  (CW)  signals.    The  ADF  receiver  is powered   through   the   2-ampere   ADF   circuit   breaker located on the overhead circuit breaker panel. b.          ADF     Control     Unit     Operating     Controls, Indicators, and Functions.  All operating controls for the ADF receiver are located on the ADF control unit. (1)  Frequency  Display.    Indicates  the  frequency to which the ADF receiver is tuned. (2)  TEST  Button.    Activates  diagnostic  self-test when pressed. (3)   TONE/OFF   Switch.      Permits   operation   of output tone when signal is received. (4) Tuning Control.  Selects operating frequency. (5)   OFF/ANT/ADF   Switch.      The   OFF   position removes    power    from    the    system.        ANT permits  operation  as  an  audio  receiver  only. ADF  permits  automatic  direction  finding  or homing operation. c.  Normal Operation. 1.  Power and mode switch - ANT or ADF. 2.  Tuning knobs - Set desired frequency. 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 tuned 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   due   to   signal   loss.      c. TONE  function  Position  the  TONE/ OFF   switch   to   TONE.      A   1000-Hz tone will identify keyed CW stations. 3.  Self-Test. a.  Power and mode switch - ADF. b.    Tuning  knobs  Tune  a  nearby  NDB, outer marker, or broadcast station. c.    TEST  switch  Depress.    RMI  pointer will     rotate     90     degrees     from     the previous   valid   indication.      Release the  TEST  switch  and  verify  that  the RMI pointer returns to that indication. NOTE If the signal received is weak or of poor quality, the bearing pointer rotation will be slow. 3-25.  TACAN SYSTEM (AN/ARN-154). a.  Description.    The  TACAN  (FIG.  3-17)  system operates   in   conjunction   with   TACAN   and   VORTAC ground stations to provide distance, groundspeed, time to  station,  and  bearing  to  station.    It  operates  in  the  L band    1000    MHz    frequency    range    on    one    of    252 preselected frequencies, 126 X mode and 126 Y mode channels.  Course deviation and distance to TACAN or VORTAC stations are displayed on the HSI.  Distance, time  to  station,  and  groundspeed  are  displayed  on  the TACAN  digital  display.    The  groundspeed  and  time  to station, are accurate only if the aircraft is flying directly toward  the  ground  station  at  a  sufficient  distance  that the slant range and ground range are nearly equal.  The system  is  protected  a  2-ampere  circuit  breaker  in  the AVIONICS portion of the overhead circuit breaker panel labeled TACAN. 3-31