TM 1-1510-224-10 (12)Compare  annunciator.    An  annunciator placarded ACT momentarily illuminates when frequencies  are  being  changed.    The   ACT   annunciator flashes if the actual radio frequency which the receiver is tuned  to  is  not  identical  to  the  frequency  shown  in  the active frequency display. c. Operating Procedures. WARNING It is not practical to provide monitoring for all conceivable system failures and, it is possible    that    erroneous    operation    could occur   without   a   fault   indication.      It   is   the responsibility  of  the  pilot  to  detect  such  an occurrence  by  means  of  cross-checks  with redundant or correlated information available in the cockpit. (1)   Equipment  turn  on.    The  ADF  receiver and  the  control  unit  are  turned  on  by  rotating  the  power and  mode  switch  on  the  ADF  control  unit  to  the    ANT, ADF, or   TONE   position.      After   power   is   applied,   the control    unit    displays    the    same    active    and    preset frequencies  that  were  present  when  the  equipment  was last turned off. (2)   Frequency selection. Frequency selection   is   made   using   either   the   frequency   select knobs or the XFR/MEM (transfer/memory recall switch). For  future  developments,  the  control  unit  has  a normal    frequency    range    of    190.00    to    1799.5    kHz. However,    when    used    with    the    ADF-60,    the    upper frequency  is  limited  to  1749.5  kHz.    Rotation  of  either frequency    select    knob    increases    or    decreases    the frequency  in  the  preset  frequency  display.    The  larger outer knob changes the frequency in 1000-kHz and 100- kHz increments (first and second numbers from the left). The  smaller  inner  knob  changes  the  frequency  in  10's, units,  and  tenths  kHz  increments  (third,  fourth,  and  fifth numbers  from  the  left).    After  the  desired  frequency  is set in the preset frequency display, it can be transferred to  the  active  frequency  display  by  momentarily  setting the XFR/MEM switch to XFR.  At the same time that the preset  frequency  is  transferred  to  the  active  display,  the previously  active  frequency  is  transferred  to  the  preset display.    The   ACT   annunciator   on   the   control   flashes while the receiver is tuning to the new frequency. NOTE If  the  ACT  annunciator  continues  flashing,  it indicates that the receiver is not tuned to the frequency displayed in the active display. The ADF control unit has a memory that permits storing   up   to   four   preset   frequencies.      Once   stored, these  frequencies  can  be  recalled  to  the  preset  display by positioning the XFR/MEM switch to the  MEM position. The   storage   location  ( CH  1   through    CH   4 )      for   the recalled  frequency  is  displayed  in  the  active  frequency display while the   XFR/MEM  switch  is  held  in  the   MEM position.    All  four  stored  frequencies  can  be  displayed one    at    a    time    in    the    preset    display    by    repeatedly positioning the   XFR/MEM  switch  to  the   MEM  position. After  the  desired  stored  frequency  has  been  recalled  to the   preset   display,   it   can   be   transferred   to   the   active display by momentarily positioning the  XFR/MEM switch to    the    XFR    position.        During    normal    operation,    all frequency   selections   and   revisions   are   done   in   the preset frequency display.  However, the active frequency can   be   selected   directly   as   described   in   the   following paragraph. (3)   Direct  active  frequency  selection.    The active    frequency    can    be    selected    directly    with    the frequency select knobs by pushing the  ACT switch for 2 seconds.        The    active    frequency    selection    mode    is indicated   by   dashes   appearing   in   the   preset   display. The  ACT  annunciator  will  flash  as  the  frequency  select knobs are turned to indicate that the transceiver is being retuned. NOTE If  the  ACT  annunciator  continues  flashing,  it indicates that the receiver is not tuned to the frequency displayed in the active display. To    return    to    the    preset    frequency    selection mode,  push  the  ACT  switch  again  for  2  seconds.    As  a safety feature, the ADF receiver control unit automatically  switches  to  the  active  frequency  selection mode  when  a  frequency  select  knob  is  operated  while the  STO,  TEST, or  XFR/MEM  switches  are  actuated,  or the memory recall inputs to the control are grounded. (4)   Frequency  storage.      Up   to   four   preset frequencies  can  be  stored  in  the  memory  in  the  ADF receiver  control  unit  for  future  recall.    To  program  the memory,  select  the  frequency  in  the  preset  frequency display  using  the  frequency  select  knobs  and  push  the STO  switch  once.    One  of  the  channel  numbers  (CH  1 through    CH   4)   will   appear   in   the   active   display   for approximately    five    seconds.        During    this    time    the channel  number  can  be  changed  without  changing  the preset frequency by momentarily positioning the XFR/MEM switch to the MEM position.  After the desired channel   number   has   been   selected,   push   the    STO switch again to store the frequency. 3-63