TM 1-1510-224-10 9. IDENT-MIC-OUT    switch    Press    to IDENT momentarily. 10. MODE 4 TEST-ON-OUT switch TEST. 11. Observe that the TEST GO annunciator illuminates. 12. MODE 4 TEST-ON-OUT switch ON. 13. ANT switch  BOT. 14. Repeat  steps  4,  5  and  6.    Observe that TEST GO indicator illuminates. 15. TOP-DIV-BOT-ANT switch TOP. 16. Repeat step 14. 17. TOP-DIV-BOT-ANT switch DIV. 18. Repeat step 14. 19. When possible, obtain the cooperation of an interrogating station  to  exercise  the   TEST  mode. Execute the following steps: 20. RAD TEST-OUT switch RAD TEST. 21. Obtain  verification  from  interrogating station  that   TEST  MODE   reply   was received. 22. RAD TEST-OUT switch OUT. (4) Transponder set identification-position operating   procedure:       The   transponder   set   can   make identification-position    replies    while    operating    in    code Modes  1,  2,  and/or  3/A,  in  response  to  ground  station interrogations.    This  type  of  operation  is  initiated  by  the operator as follows: 1. Modes    1,    2    and/or    3/A    ON,    as required. 2. IDENT-OUT-MIC switch Press momentarily to IDENT, when directed. NOTE Holding circuits within the transponder  receiver-transmitter  will transmit identification-position signals  for  15  to  30  seconds.    This  is normally   sufficient   time   for   ground control to identify the aircraft's position.    During  the  15  to  30  second period,    it    is    normal    procedure    to acknowledge via the aircraft communications set that identification/    position    signals    are being generated. Set any of the  M1, M2, M3/A, M-C, or  MODE  4  switches to   OUT   to   inhibit   transmission   of   replies   in   undesired modes. With the  IDENT-OUT-MIC switch set to the  MIC  position, the  POS  IDENT  button  on  either  control  wheel  must  be depressed to transmit identification pulses. (5) Shutdown procedure: 1. To   retain   Mode   4   code   in   external computer during a temporary shutdown: 2. MODE   4   CODE    switch    Rotate    to HOLD. 3. Wait 15 seconds. 4. MASTER control OFF. 5. To  zeroize  the  Mode  4  code  in  the external    computer,    turn     MODE    4 CODE switch to ZERO. 6. MASTER    control    OFF.        This    will automatically zeroize external computer   unless   codes   have   been retained (step 1 above). 3-34.  PILOT'S BAROMETRIC ALTIMETER INDICATOR (BA-141). The pilot's barometric altimeter indicator (fig.  3-35), is a servoed unit which displays altitude information from the air  data  computer.    Altitude  is  displayed  by  a  10,000  foot counter,  a  1000  foot  counter,  a  100  foot  counter,  and  a single  needle  pointer  (coupled  with  the  100  foot  counter) which indicates hundreds of feet on a circular scale in 20 foot   increments.      Below   an   altitude   of   10,000   feet,   a diagonal   striped   symbol   will   appear   on   the   10,000   foot counter.      The   barometric   pressure   knob   allows   ground supplied  altimeter  setting  to  be  manually  set.    Altimeter setting  is  displayed  in  inches  of  mercury  and  millibars  on barometric counters. a. Controls, Indicators and Functions. (1) Failure   warning   flag.      The   failure   warning flag,   placarded   OFF,   comes   into   view   when   the   error between  the  altitude  displayed  and  the  signal  received  is too   great,   the   air   data   computer   goes   invalid,   or   the barometric     altimeter     loses     primary     power.          Pilot's Barometric Altimeter Indicator (2) Altitude alert annunciator.  The altitude alert annunciator, placarded   ALT,  is  illuminated  when  aircraft is  within  1000  feet  of  preselected  altitude  during  capture maneuver   and   extinguishes   when   aircraft   is   within   250 feet  of  preselected  altitude.    After  capture,  annunciator will 3-90