TM 55-1510-222-10 and/or  observe  (for  Mode  4  interrogations  and replies). 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   the 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: a. RAD TEST-OUT switch - RAD TEST. b. Obtain verification from interrogating station that a TEST MODE reply was received. c. 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 Ml, 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  must  be  depressed to transmit identification pulses. (5)   Shutdown procedure: 1. To   retain   Mode   4   code   in   external   computer during a temporary shutdown: a. MODE 4.  CODE switch - Rotate to HOLD. b. Wait 15 seconds. c. MASTER control - OFF. 2. To   zeroize   the   Mode   4   code   in   the   external computer, turn MODE 4 CODE switch to ZERO. 3. MASTER control - OFF.  This will automatically zeroize  the  external  computer  unless  codes  have  been retained (step 1 above). d. Transponder    -    Emergency    Operation.        Not applicable. 3-33. PILOT'S ALTIMETER INDICATOR. The pilot's altimeter (fig.  3-26), in the upper left side of the instrument panel, is a servoed unit, under control of   the   Air   Data   Computer   and   is   part   of   the   Flight Director/Autopilot   system.      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  pressure  values  to  be  adjusted and displayed in inches Hg or millibars.  If AC power to the  altimeter  is  lost,  a  warning  OFF  flag  will  appear  in the   upper   counter   drum   display   window   to   indicate power  loss,  unreliable  altimeter  readings,  and  possible loss    of    encoder    transmissions    to    ground    stations. Circuits are protected by a 3-ampere fuse in the junction box.      When   the   BARO   knob   is   adjusted   to   ground supplied instructions, the updated altitude pressure is 3-80