TM 1-1510-225-10 3A-44 (5)   TACAN  Units  Digits,  NAV  Kilohertz,  and TACAN X Or Y Tuning Knob.  The TACAN units digits, NAV  kilohertz,  and  TACAN  X  or  Y  tuning  knob  is  the larger  of  the  two  knobs  that  are  used  to  set  the  NAV frequency or TACAN channel in the standby frequency display.  Rotation of this knob sets the three digits to the  left  of  the  decimal  point  in  the  standby  frequency display   or   the   10's   and   100's   digits   of   a   TACAN channel    depending    on    the    selected    mode.        The numbers will roll over at the upper and lower frequency or channel limits. (6)   Channel   Switch.      The   channel   switch, placarded   CHAN,   is   a   push-button  switch,  which  is used to select whether TACAN channel or frequency is used in the active frequency or channel display. (7)   Power  and  Volume  Control.    The power and  volume  control  placarded   OFF  /  VOL,  controls operation   of   the   receiver   control   unit.      Clockwise rotation   from   the  OFF  position  applies  power  to  the system   and   continued   clockwise   rotation   increases volume. (8)   Standby Frequency Display.  Displays the standby (inactive) frequency or channel. c.   Operating Procedures.  (1)   Equipment  Turn-On.      The  receiver  and the  control  unit  are  turned  on  by  clockwise  rotation  of the power and volume knob. (2)   Frequency Selection. (a)   Standby     Frequency Entry Mode.   When   the   receiver   control   unit   is   in   the   standby frequency or channel entry mode, the active frequency or channel, in the active frequency or channel display, is  selected  by  changing  the  frequency  or  channel  in the   standby   frequency   display.      Then   transfer   the selected frequency or channel to the active display by pressing    the    transfer    switch.        The    frequency    or channel in the standby frequency or channel display is changed by means of the tuning knobs on the control unit.        The    control    unit    will   remain   tuned   to   the frequency  or  channel  in  the  active  display  as  long  as the control unit is in the standby entry mode. (b)   Active Frequency Entry Mode.  When the  receiver  control  unit  is  in  the  active  frequency  or channel  entry  mode,  the  active  frequency  or  channel (in the active frequency or channel display) is changed directly  by  rotating  the  tuning  knobs.    The  receiver control   unit   is   changed   to   the   active   frequency   or channel selection mode by holding the transfer switch pressed   for   longer   than   2   seconds.      Momentarily pressing  the  transfer  switch  will  change  the  receiver control  unit  back  to  the  standby  entry  mode  and  will return the standby frequency or channel display to the frequency  or  channel  displayed  before  entering  the active mode. 3A-26.  AUTOMATIC     DIRECTION    FINDER    (ADF) RECEIVER (KDF 806). a.   Description.      The   ADF   receiver   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   to   1750   kHz.      In   the   ANT   mode,   the   ADF receiver  functions  as  an  aural  receiver,  providing  only an aural output of the received signal.  In 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  ADF  receiver  is powered through a 2-ampere circuit breaker, placarded  ADF,  located  on  the  right  sidewall  circuit breaker panel, Figure 2-6. b.  ADF    Control    Unit    Operating    Controls, Indicators, and Functions.   Refer to Figure 3A-21. (1)   Active  Frequency  Display.    Displays the active  frequency  (frequency  to  which  the  receiver  is tuned). (2)   Photocell. The built-in photocell automatically controls display brightness. (3)   Frequency Transfer Switch. The frequency transfer switch is a push-button switch that transfers  the  frequency  in  the  standby  display  to  the active  display  and  the  frequency  in  the  active  display to the standby display each time it is pressed. Pressing  the  frequency  transfer  switch  for  more than  2  seconds  while  in  the  standby  entry  mode  will switch   the   receiver   control   unit   to   the   active   entry mode. Momentarily    pressing    the    frequency    transfer switch  while  in  the  active  entry  mode  will  return  the receiver control unit to the standby entry mode. (4)   Kilohertz    (100's)    Tuning    Knob.        The kilohertz    100's    tuning    knob    is    the    larger    of    two concentric knobs, which are used to set the frequency in   the   standby   frequency   display.      Rotation   of   the larger tuning knob sets the 100's kilohertz digits in the standby frequency display.  The numbers will roll over at the upper and lower frequency limits.  Rotating the kilohertz 100's tuning knob in either direction with the receiver  control  unit  in  the  channel  mode  will  change the channel number and its corresponding frequency.