TM 55-1510-220-10 line  position  will  be  displayed  in  degrees  in  the  upper  left corner  of  the  screen.    The  line  will  disappear  approximately 15   seconds   after   the   switch   is   released.      It   will   then automatically return to "0" degrees. (7) HOLD   switch.      Push   type   on/off   switch. When activated, the last image presented before pressing the switch  is  displayed  and  held.  The  word  HOLD  will  flash  on and  off  in  the  upper  left  corner  of  the  screen.    Pressing  the switch again will update the display and resume normal scan operation. (8) Function  switch.    Controls  operation  of  the radar set. (a) OFF. Turns set off. (b) STBY.  Places set in standby mode. This position  also  initiates  a  90-second  warm-up  delay  when  first turned on. (c) TEST.    Displays  test  pattern  to  check for  proper  operation  of  the  set.    The  transmitter  is  disabled during this mode. (d) ON.  Places set in normal operation. (9) MODE   switches.      Momentary   action   type switches.  Pressing and holding either switch will display an information  list  of  operational  data  on  the  screen.    The  data heading will be in blue, all data except present data will be in yellow, and present selected data will show in blue.  The three weather levels will be displayed in red, yellow, and green.  If WXA  mode  has  been  selected,  the  red  bar  will  flash  on  and off.  If the switch is released and immediately pressed again, the   mode   will   increase   or   decrease   depending   on   switch pressed.    When  either  top  or  bottom  mode  is  reached,  the opposite switch must be pressed to further change the mode. (10) NAV    switch.        If    pressed    with    the    INS operating   and   the   weather   radar   operating   in   a   weather depiction  mode,  the  screen  will  display  INS  waypoints  that are located within the range displayed and within the degree of coverage left or right of the present heading of the aircraft. (11) BRT     control.          Used     to     adjust     screen brightness. c. Weather Radar Normal Operation. WARNING Do not operate the weather radar set while personnel   or   combustible   materials   are, within   18   feet   of   the   antenna   reflector When  the  weather  radar  set  is  operating, high-power    radio    frequency    energy    is emitted  from  the  antenna  reflector,  which can   have   harmful   effects   on   the   human body and can ignite combustible materials. CAUTION Do  not  operate  the  weather  radar  set  in  a confined   space   where   the   nearest   metal wall  is  50  feet  or  less  from  the  antenna reflector.      Scanning   such   surfaces   may damage receiver crystals. (1) Turn-on procedure: Function switch TEST or ON,  as  required.    (Information  will  appear  after  time  delay period has elapsed.) (2) Initial adjustment operating procedure: 1. BRT control As required. 2. MODE  switches  Press  and  release  as required. 3. RANGE  switches  Press  and  release  as required. 4. TILT   control   Move   up   or   down   to observe  targets  above  or  below  aircraft level.  The echo display will change in shape and location only. (3) Test procedure: 1. Function switch TEST. 2. RANGE switches- Press and release as required to obtain 80-mile display. 3. BRT control As required. 4. Screen Verify proper display.  (The test display   consists   of   two   green   bands, two yellow bands, and a red band on a 120-degree scan.  The word TEST will be displayed in the upper 3-79