TM 1-1510-225-10 3B-197 the    CRT    display    on    the    instrument    panel    as    an individual discharge point (+). b.  Controls and Functions.  (1)   Power/Brightness Control.  Rotate to turn on the system and adjust the brightness of the display. (2)   Selector Buttons.  The specific function of each button is displayed adjacent to the button in each operating mode. c.   Normal Operation. (1)   Self-Test.  Each time the system is turned on  it  will  automatically  cycle  through  a  series  of  self- tests    which    ensure    that    all    major    functions    are operating properly. These tests, which take approximately 15 seconds to complete, check antenna reception, processor circuitry calibration, memory and microprocessor  function,  and  proper  operation  of  the options.    After  proper   operation  has  been  verified  by the  self-test  program,  a  confirmation  message,  ALL TESTS  ARE  OK,  will  display  in  reverse  video.    This message  will  remain  on  the  display  for  approximately 3 seconds and then will be replaced automatically with MAIN MENU. If  the  system  fails  any  of  the  internal  tests,  an error  message  will  appear  indicating  which  test  failed and   which   functions   may   be   inoperative.      In   most cases,  all  other  systems  will  continue  to  operate.    If continued operation is possible, the message, PRESS ANY KEY TO CONTINUE will display. When    initially    turned    on,    the    system    may complete its self-test  program  before  the  CRT  comes on.    In  that  case  it  is  possible  that  the  first  message that  will  be  seen  is  the  main  menu.    This  is  normal operation. If  the  weather screen is selected immediately, it is  possible  the  advisory  message  FLAG  will  display where heading information is normally displayed.  This usually means the gyro system has not yet come up to speed.        FLAG    should    be    replaced    with    heading information momentarily. (2)   Main   Menu.    The  main  menu  provides access  to  the  two  weather  mode  views  and  additional system functions, including checklists, time/date information,  options,  and  navaid  display.    To  select  a specific menu item, press  NEXT button on the display until the desired item is highlighted and press the  GO button to view the selected menu item. (3)   Weather   Modes.      Two   weather   mode views  are  available  from  the  main  menu  by  pressing either  the  360°  or  the  120°  button.    The  symbol   Ü means to "go to."  When the weather mode is initially selected,   it   will   always   be   in   the   200-nm   range.   Pressing the button beside the range setting will cycle through the additional range selections from 200 nm to 100 nm to 50 nm to 25 nm and back to 200 nm.  The 25-nm  range  is  indicated  by  a  solid  ring  to  advise  of close proximity to potential thunderstorms.  Either view can  be  selected  from  the  main  menu  or  the  opposite view.    When  changing  from  one  view  to  another,  the range remains constant. The   120°   view   provides   an   expanded   view so thunderstorm information is displayed in greater detail.   Refer to Figure 3B-154. Figure 3B-154.  120° Weather Mode Press the   CLEAR  button  to  erase  all  weather data   from   the   display   and   system   memory.      The intensity  of  a  thunderstorm  can  be  identified  by  the speed  with  which  the  discharge  points  appear.    The system    continually    receives    and    processes    new electrical    discharge    information.        Monitor    this    by pressing the clear button often.  The more intense the storm, the faster the discharge points reappear. Multiple discharges which appear as clusters are indicative of thunderstorm activity.  A large number of discharge  points  indicate  a  faster  rate  of  occurrence and,  therefore,  a  more  severe  thunderstorm.    Fewer discharge points indicate a smaller, but not necessarily,   weaker,   cell.      Thunderstorm   conditions change   rapidly   and   monitoring   their   activity   over   a period   of   time   by   use   of   the    CLEAR   function   is recommended.      Any   grouping   of   discharge   points within    the    25-nm    range    is    cause    for    immediate avoidance.