TM 1-1510-225-10 3B-168 (1)   Compare     Annunciator    (ACT).          ACT momentarily  illuminates  when  frequencies  are  being changed.   ACT flashes if the actual radio frequency is not   identical   to   the   frequency   shown   in   the   active frequency display. (2)   XFR   /   MEM    Switch.      This   switch   is   a 3-position, spring-loaded toggle switch.  When held to the XFR position, the preset frequency is transferred to the   active   display   and   the   receiver   re-tunes.      The previously  active  frequency  becomes  the  new  preset frequency and is displayed in the lower window.  When this switch is held to the  MEM position, one of the four stacked  memory  frequencies  is  loaded  into  the  preset display.    Successive  pushes  cycle  the   four  memory frequencies through the display (…2, 3, 4, 1, 2 ,3…). (3)   Frequency Select Knobs.  Two concentric knobs control the preset or active frequency displays.   The larger knob changes the three digits to the left of the  decimal  point  in  1-MHz  steps.    The  smaller  knob changes the two digits to the right of the decimal point 0.05-MHz  steps.    Frequencies  roll  over  at  the  upper and  lower  limits.    The  two  frequency  select  switches are independent of each other such that the upper and lower  limit  rollover  of  the  0.1-MHz  digit  will  not  cause the 1.0-MHz digit to change. (4)   ACT  Button.    Push  the    ACT  button  for approximately   2   seconds   to   enable   the   frequency select   knobs   to   directly   retune   the   receiver.      The button   window   will   display   dashes   and   the   upper window will  continue  to  display  the  active  frequency.   Push   the   ACT   button   a   second   time   to   return   the control to the normal 2-display mode. (5)   TEST Button.  Press the  TEST button to initiate the radio self-test diagnostic routine.  (Self-test is active only when the TEST button is pressed.) (6)   Light     Sensor. The built-in sensor automatically controls the display brightness. (7)   STO Button.  The  STO  button  allows  up to four preset frequencies to be selected and entered into    the    control's    memory.        After    presetting    the frequency  to  be  stored,  push  the    STO  button.    The upper     window     displays     the     channel     number     of available    memory    (CH    1    through    C4);    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 button  a  second  time  to  commit  the  preset  frequency to memory in the selected location. After approximately   5   seconds,   the   control   will   return   to normal operation. (8)   Volume   Control.      A   volume   control   is concentric with the power and mode switch. (9)   Power and Mode Switch.  The power and mode  switch  contain  three  detented  positions.    The ON   and   OFF   positions  switch  system  power.    The HLD     position    allows    the    NAV    frequency    to    be changed,   but   holds   the   DME   to   the   current   active frequency. (10)   MEM  and  HLD  Annunciators.    The  NAV control    contains    memory   (MEM)    and    hold   ( HLD) annunciators.        The    MEM    annunciator    illuminates whenever a preset frequency is being displayed in the lower window.  The  HLD annunciator indicates that the DME   is   held   to   the   active   frequency   at   time   of selection;  the  NAV  frequency  may  be  changed.    The upper  window  now  displays  the  NAV  frequency  and the lower window displays the held DME frequency. (11)   Preset   Frequency   Display.      The   preset (inactive)    frequency    and    diagnostic    messages    are displayed in the lower window. (12)   Active   Frequency   Display.      The   active frequency  (frequency  to  which  the  VIR-32  receiver  is tuned)  and  diagnostic  messages  are  displayed  in  the upper window. c.   Operating Procedures.  CAUTION 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 Startup.    The  VIR-32 receiver and  the  CTL -32 NAV control are turned on by rotating the power and mode switch on the NAV control to the ON   position.      After   power   is   applied,   the   CTL-32 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). Rotation of either frequency select knob increases  or  decreases  the  frequency  in  the  present frequency display.  The larger, outer knob changes the frequency in 1-MHz increments (number to the left of