TM 1-1510-225-10 3C-38 10.   TACAN  Indicator  –  Read range (NM). Verify  proper  range  is  represented  on HSI distance readout. 11.   If   desired   to   proceed   direct   TO   or FROM a TACAN station, or determine the   course,   rotate   the   course   knob until     the     course     deviation     bar     is centered   and   the   TO/FROM   pointer indicates TO or FROM. NOTE Always  crosscheck  the  HSI  with  the  RMI and  other  available  navaids  to  determine position. 12.   To   use   TACAN   with   pilot-controlled flight, control aircraft by manual controls,    responding    to    information displayed  on  the  flight  director,  RMI, HSI, and other instruments. 13.   To    use    TACAN    with    the    autopilot, press     AP     ENGAGE     and     monitor autopilot performance on flight director,  RMI,  and  TACAN  indicators.   Verify   adherence   to   preset   heading and course and confirm the execution of displayed steering commands. NOTE The  TACAN  groundspeed  reading  will  be accurate   only   when   the   aircraft   is   on   a course   directly   to   or   from   the   TACAN station.        When    headed    away    from    the station,     the     TACAN     indicator     minutes reading will be in error. (4)   Shutdown.   Turn  VOL / ON / OFF knob – OFF. 3C-23.  DISTANCE MEASURING EQUIPMENT (DME). a.    Introduction. The DME-42 receiver/ transmitter  and  IND-42A  indicator  can  simultaneously track   and   provide   complete   information   from   up   to three DME stations.  The information displayed on the IND-42A    includes    channel    number    (1,    2,    or    3), distance,  groundspeed,  time-to/from-station,  and  the station  identifier  including  the  identifier  of  a  DME  co- located with an ILS.  Refer to Figure 3C-18. Three-channel  operation  will  have  the  DME-42 being controlled by both CTL -32 NAV Controls.  These provide serial digital commands to operate on 1, 2, or 3 specific frequencies through the single input port of the   DME-42.      The   DME   channel   1   frequency   will always be the same as shown by the active frequency display  on  the  pilot's  side  CTL -32.    The  DME  channel 2 frequency will always be the same as shown by the active  frequency  display  on  the  copilot's  side  CTL -32.   The channel 3 frequency is the same as shown by the preset frequency display on the pilot's side CTL-32. b.    Controls, Indicators, and Functions.   Except for audio, frequency selection and the self-test switch, all operating controls for the DME system are located on the IND-42A Indicator.  Frequency selection is  accomplished  using  the  CTL-32  NAV  Control.    The DME-42   self-test   routine   can   be   initiated   using   the TEST   button   on   the   CTL -32.      DME   audio   is   only available for channels 1 and 2.  When the  DME audio selector   switch   (pilot/copilot),   located   on   the   audio control   panel,   is   in   the   up   position,   DME   audio   is available  from  either  DME  channel  1  or  2  as  selected by the  DME  AUDIO  CHAN  1 /  CHAN  2 toggle switch located  below  the  Data  NAV  control  unit.    Refer  to Figure 3C-18. 1.  Numeric Display 2.  Alphanumeric Display 3.  Light Sensor 4.  PWR Switch 5.  Mode SEL Switch 6.  CH (channel) Switch 7.  Annunciators Figure 3C-18.  IND-42A DME Indicator (1)   Numeric  Display   –  The  numeric  display presents the NM (distance) and diagnostic code. (2)   Alphanumeric Display – The alphanumeric display presents the   KT (Velocity) time- to-station  ID  (2,  3,  or   4  letter  station  identifier),  and diagnostic identifier.