TM 1-1510-223-10 NOTE After 3 or 4 seconds, simulated lightning test pulses are sent to the display. 3. Verify that a rate symbol is displayed at 25 nautical miles, at 45 degrees to right of center.  This symbol  will  take  approximately  5  to  7  seconds  to  build up. NOTE This time will be extended to approximately 15 seconds if   TST   is   selected   immediately   from   OFF,   due   to lightning processor initialization. The symbol's range may vary by as much as 5 nautical miles if strong local interference is present. 4. Verify   that   a   magenta   lightning   alert symbol  is  displayed  at  maximum  selected  range,  at  45 degrees right of center.  This must remain on display for 3 to 7 seconds. 5. To  restart  the  test  switch  to  LX  mode and back to CLR/TST mode. If   the   power-on   test   or   the   on   line   built-in   test equipment  detects  a  fault,  either  prior  to  or  during  the operation    of    self    test,    the    system    will    switch    the displayed  mode  symbol  to  an  amber  LX/F.    A  special fault   message   may   be   obtained   by   switching   to   the CLR/TST mode.  In the CLR/TST mode an amber LXmn will  be  displayed,  where  mn  is  a  failure  code  that  may be interpreted according to table 3-13. g. Lightning Sensor System Normal Operation. 1. LSS mode selector switch (radar control panel) -LX 2. Range  switches  (radar  control  panel)  - Set desired range. NOTE If radar system mode selector switch is set to OFF, LSS range will revert to 50 nautical miles. 3-33. TRANSPONDER SET (APX-100). a. Description. The transponder system receives,  decodes,  and  responds  to  interrogations  from air     traffic     control     (ATC)     radar     to     allow     aircraft identification,  altitude  reporting,  position  tracking,  and emergency tracking.  The system receives a frequency of 1030 MHz and transmits preset coded reply pulses on a frequency of 1090 MHz at a minimum peak power of 200 watts.  The range of the system is limited to line-of- sight.    The  transponder  system  consists  of  a  combined receiver/transmitter/control  panel  (fig.  3-34)  located  in the pedestal extension; a pair of remote switches, one in each  control  wheel;  and  two  antennas,  located  on  the underside   and   top   of   the   fuselage.      The   system   is protected  by  the  3-ampere  TRANSPONDER,  and  35- ampere    AVIONICS    MASTER    PWR    No.        1    circuit breakers on the overhead circuit breaker panel (fig.  2- 7). b. Transponder Controls, Indicators, and Functions (fig.  3-34). (1) TEST-GO    indicator.       illuminates    to indicate successful completion of built-in-test (BIT). (2) TEST-MON   indicator.      Illuminates   to indicate system malfunction or interrogation by a ground station. (3) ANT  switch.    Selects  desired  antenna for signal input (a) TOP.  Selects upper antenna. (b) DIV.     Selects     diverse     (both) antennas. (c) BOT.  Selects lower antenna. (4) RAD TEST-OUT switch.  Enables reply to TEST mode interrogations from test set. (5) MASTER  CONTROL.   Selects  system operating mode. (a) OFF.  Deactivates system. (b) STBY.     Activates  system  warm- up (standby) mode. (c) NORM. Activates normal operating mode. (d) EMER.       Transmits    emergency reply code. (6) STATUS ANT indicator.   Illuminates to indicate the BIT or MON fault is caused by high VSWR in antenna. (7) KIT.   Illuminates to indicate the BIT or MON fault is caused by external computer. (8) STATUS  ALT  indicator.   Illuminates  to indicate the BIT or MON fault is caused by the altitude digitizer. 3-85