TM 1-1510-225-10 3A-42 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)   Megahertz Tuning Knob.   The megahertz tuning  knob  is  the  larger  of  two  concentric  knobs  that are used to set the frequency in the standby frequency display.    Rotation  of   the  megahertz  tuning  knob  sets the  three  digits  to  the  left  of  the  decimal  point  in  the standby frequency display.  The numbers will roll over at the upper and lower frequency limits.  Rotating the megahertz tuning knob in either direction with receiver control   unit   in   the   channel   mode   will   change   the channel number and its corresponding frequency. (5)   Kilohertz   Tuning   Knob.      The   kilohertz tuning knob is the smaller of two concentric knobs that are used to set the frequency in the standby frequency display.  Rotation of the kilohertz tuning knob sets the two   digits   to   the   right   of   the   decimal   point   in   the standby  frequency  display  in  50  kilohertz  increments.   The   numbers   will   roll   over   at   the   upper   and   lower frequency limits.  Rotating the kilohertz tuning knob  in either direction with receiver control unit in the channel mode     will     change     the     channel     number     and     its corresponding frequency. (6)   Channel   Switch.      The   channel   switch, placarded  CHAN, is a push-button switch that will put the  receiver  control  unit  into  the  channel  mode  when momentarily pressed, or into the program mode when pressed for more than 2 seconds. (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. 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   entry   mode,   the   active   frequency   (in   the active  frequency  display)  is  selected  by  changing  the frequency    in    the    standby    frequency    display,    then transferring    the    selected    frequency    to    the    active frequency  display  by  pressing  the  frequency  transfer switch.        The    frequency    in    the    standby    frequency display  is  changed  by  means  of  the  megahertz  and kilohertz tuning knobs on the receiver control unit.  The receiver control unit will remain tuned to the frequency in the active frequency display as long as the receiver control unit is in the standby frequency entry mode. (b)   Active Frequency Entry Mode.  When the receiver control unit is in the active frequency entry mode,  the  active  frequency  (in  the  active  frequency display)  is  changed  directly  by  rotating  the  kilohertz and megahertz tuning knobs.  The receiver control unit is  changed  to  the  active  frequency  selection mode by holding   the   transfer   switch   pressed   for   longer   than 2 seconds.          Momentarily     pressing     the     frequency transfer  switch  will  change  the  receiver  control  unit back  to  the  standby  entry  mode  and  will  return  the standby  frequency  display  to  the  frequency displayed before entering the active frequency mode. (c)   Channel Mode. Pressing the channel switch, placarded   CHAN, will put the receiver control unit into the channel mode.  When the receiver control   unit   is   in   the   channel   mode,   the   channel number  is  displayed  in  the  active  frequency  display and the channel frequency is displayed in the standby frequency  display.    Channel  frequencies  have  to  be set with the unit in the program mode. When  the  receiver  control  unit  is  in  the  channel mode,  the  receiver  will be tuned to the frequency that is  displayed  in  the  standby  frequency  display.    If  no channels have been programmed, the receiver control unit  will  display  channel  1  (CH  1)  with  dashes  in  the standby frequency display for 5 seconds, then the unit will tune the receiver to the last frequency displayed in the active frequency display. Pressing  the  transfer  switch  for  2  seconds  will change the receiver control unit to the active frequency entry mode. (3)   Program   Mode.        The    frequencies    and channel  numbers  used  in  the channel mode must be programmed into memory with the receiver control unit in the program mode.  Pressing the  CHAN switch for longer than 2 seconds will put the receiver control unit into the program mode.  The channel number that was last   used   will   be   displayed   and   flash   in   the   active frequency display.  With the channel number flashing, rotating   the   tuning   knobs   will   change   the   channel number.      A   channel   number   with   no   programmed frequency  will  have  dashes  in  the  standby  frequency