TM 1-1510-224-10 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  a  2-ampere  circuit  breaker  placarded ADF,  located  on  the  overhead  circuit  breaker  panel  (fig. 2-9). b.        ADF    Control    Unit    Operating    Controls, Indicators, and Functions.    All  operating  controls  for  the ADF  receiver  are  located  on  the   ADF  control  unit  (fig. 3-25). (1)   Active   frequency   display.      The   active frequency   (frequency   to   which   the    ADF    receiver    is tuned)   and   diagnostic   messages   are   displayed   in   the upper window. (2)   Transfer/memory switch.    This  switch  is a    3-position    spring-loaded    toggle    switch    placarded XFR/MEM,    which,    when    held    to    the    XFR    position, causes  the  preset  frequency  to  be  transferred  up  to  the active display and the   ADF  receiver  to  be  retuned.    The previously  active  frequency  will  become  the  new  preset frequency   and   will   be   displayed   in   the   lower   window. When this switch is held to the  MEM position, one of the four stacked memory frequencies will be loaded into the preset  display.    Successive  pushes  will  cycle  the  four memory frequencies through the display. (3)   Store   switch.      This   switch,   placarded STO, allows up to four preset frequencies to be selected and    entered    into    the    control    unit's    memory.        After presetting   the   frequency   to   be   stored,   push   the   STO switch.  The upper window displays the channel number of  available  memory  (CH  1 through   CH  4);   the   lower window  continues  to  display  the  frequency  to  be  stored. For  approximately  5  seconds,  the   MEM  switch  may  be used  to  advance  through  the  channel  numbers  without changing  the  preset  display.    Push  the   STO  switch  a second  time  to  commit  the  preset  frequency  to  memory in the selected location.  After Table 3-7.  VHF Navigation Receiver Fault Codes CODE INCORPORATION COMMENT 00 No fault found 02 RAM test failed Unit unusable (mP problem) 03 No serial data to unit Unit unusable (CTL problem) 04 No serial freq word Unit unusable (CTL problem) 05 Invalid NAV freq CTL may be tuned to DME channel 06 Microprocessor fault Unit unusable 09 Microprocessor fault Unit unusable 10 Microprocessor fault Unit unusable 11 AID fault Unit unusable 12 AID failed accuracy test Unit unusable 13 +13 V dc power supply fault Unit unusable 14 -13 V dc power supply fault Unit unusable 15 VOR sin 0 / GS D/A fault VOR/LOC unusable 16 VOR cos 0 /GS D/A fault VOR/GS unusable 17 VOR smo unlocked VOR receiver imperative 18 VOR AFC not locked VOR unusable (no rf signal) 19 Low 30 Hz reference signal VOR unusable 20 Low 30 Hz variable signal VOR unusable 21 400 Hz pwr supply unusable VOR OBI and OBS unusable 22 OBI sin out of tolerance VOR OBI and OBS unusable 23 OBI cos out of tolerance VOR OBI and OBS unusable 24 OBS return out of tolerance VOR OBS unusable 25 LOC smo unlocked LOC receiver inoperative 26 LOC signal level low LOC unusable 27 LOC dev out of tolerance LOC dev unreliable 28 GS smo unlocked GS receiver inoperative 29 GS signal too low GS unusable 30 GS dev out of tolerance GS dev unreliable 32 Marker beacon fault Observe marker lamps for fault BT03844 3-61