TM 55-1510-222-10 concentric  knob  to  select  the  channel  and  repeat  the steps. 21. To return to an operating mode, push the PGM button. NOTE The mode for each channel (LSB, USB or    AM)    is    stored    along    with    the frequency.  If the mode is changed, the system will receive and transmit in the mode selected for transmit. d. Shutdown.  OFF/VOLUME switch OFF. e. HF   Command   Set   Emergency   operation. Not applicable. 3-12.  SINCGARS AN/ARC-201(V). a. Description.    The  Sincgars  AN/ARC-201(V) radio    system    (fig.        3-5)    provides    VHF-FM    radio communications, in single channel and ECCM mode of operation.  The frequency range is 30 to 87.  975 MHz channelized in tuning increments of 25 kHz.  In addition a frequency offset tuning capability of -10 kHz, -5 kHz, 5  kHz  and 10  kHz  is  provided  in  both  receive  and transmit modes; this capability is not used in the ECCM mode.    The  system  provides  improved  immunity  from the threat of electronic warfare, and provides for secure communication    of    voice    and    data    signals    through interfacing with the KY-58.  The system is protected by a 10-ampeire  circuit  breaker,  placarded  FM,  located  on the overhead circuit breaker panel. The   Sincgars   FM   radio   set   is   a   combination control/transceiver,  installed  in  the  pedestal  extension for  convenient  operation  by  the  pilot  or  copilot.    The front panel control allows the pilot or copilot to instantly switch to any one of 20 preset channels. b. Controls and functions. NOTE The IFM RF PWR switch is not used on this installation (1) Function Switch.  The function switch is  used  to  select  the  basic  operational  condition  within the  radio  transceiver  (RT).    It  is  a  nine-position  switch with positions one, eight, and nine being isolated switch positions.    Isolated  switch  positions  require  a  pull  and turn operation to actuate.  Position one is OFF, eight is Z-A   (zero   all)   and   position   nine   is   STOW   (storage). Actions initiated by these switch settings are sensitive to the  operation  of  the  RT  and  are  therefore  designed  to require  a  conscious  effort  of  the  operator  to  actuate. Operative positions of the function switch are as follows: (a) OFF.        All    primary    power    is removed  from  the  RT.    The  memory  holding  battery, however,    is    connected    to    its    associated    circuitry, providing   the   retention   of   stored   frequency   hop   (FH) parameters, time and preset frequencies. (b) TEST.        When    selected,    the major  components  of  the  subsystem  are  examined  to verify  their  operation.    The  RT  and  the  ECCM  module are   both   tested   under   micro-processor   control.      The results  of  the  self-tests,  as  well  as  the  presence  of  the ECCM    module,    are    presented    on    the    front    panel displays. (c) SQ  ON  (Squelch  On).    Primary power is applied and operation will be by normal, locally controlled actions.  The squelch is enabled and the RT operation  modified  by  other  front  panel  controls.    The radio's receiver audio output is connected to the No.  2 communications   receiver   switch   of   the   audio   control panel.    Keying  of'  the  transmitter  is  accomplished  by pressing   the   Control   Wheel   switch,   placarded   INPH XMT MIC, to the second (XMT) level. (d) SQ OFF (Squelch Off). Operation  of  the  RT  with  the  switch  in  this  position  is identical  to  the  ON  position  except  the  squelch  circuits are  disabled.    This  position  provides  the  capability  to communicate at extremely low input levels if required. (e) LD    (Load).        In     this     switch position, all primary power is applied to the RT and the transmitter  is  enabled.    With  the  function  switch  in  LD, loading of preset frequencies is accomplished by normal keyboard entry in conjunction with the PRESET switch. Also, time may be set with the switch in LD.  ECCM net parameters and lockout channels are also filled with the switch in this position, providing an ECCM module is in the  RT,  by  connecting  the  appropriate  fill  device  to  the FILL connector and pressing the keyboard H LD button once. (f) LD-V   (Load   Variable).      When selected the TRANSEC variable is loaded into the RT providing   an   ECCM   module   is   in   the   RT.      The   fill device  is  connected  as  in  LD  and  the  keyboard  H  LD button pressed once to initiate the transfer. (g) Z-A    (Zero    All).        This    switch position is 3-12