TM 1-1510-225-10 2-114 Table 2-10.  Airspeed Indicator NO. FUNCTION 1 Displays TAS. 2 Displays SAT in Two digits and  6 sign from  – 99 °C to + 50 °C. 3 Dims Front Panel. 4 Momentary push button when pressed changes SAT to TAT. 2-79.  STANDBY BAROMETRIC ALTIMETER. a.   Description. The standby barometric altimeter,    illustrated    in    Figure    2-36,    provides    an indication  of  the  aircraft's  pressure  altitude above sea level. NOTE If the altimeter does not read within 70 feet of  field  elevation,  when  the  correct  local barometric   setting   is   used,   the   altimeter needs   calibration   or   internal   failure   has occurred.  An error of greater than 70 feet also  nullifies  use  of  the  altimeter  for  IFR flight. b.  Controls, Indicators, and Functions. (1)   Altitude  Scale.    Used  in  conjunction  with altitude  indicator  needle  to  indicate  aircraft  altitude  in hundreds of feet, subdivided into 20-foot increments. (2)   Counter-Drum Altitude Display.  Indicates aircraft  altitude  in  tens  of  thousands,  thousands,  and hundreds of feet above sea level. (3)   Altitude     Indicator     Needle.          Used     in conjunction    with    altitude    scale    to    display    aircraft altitude in hundreds of feet. (4)   Barometric Pressure Setting Knob.  Used to  manually  set  barometric  pressure  displayed  in  the IN HG display. (5)   Barometric  Pressure  Display  (Inches  of Mercury).  Indicates the barometric pressure in inches of   mercury   that   has   been   set   by   the   barometric pressure setting knob. 1.  Altitude Scale 2.  Counter-Drum Altitude Display 3.  Altitude Indicator Needle 4.  Barometric Pressure Setting Knob 5.  Barometric   Pressure   Display   (Inches   of Mercury) Figure 2-36.  Standby Barometric Altimeter 2-80.  ALTIMETERS. a.   Pilot's    Servoed    Altimeter.        The    pilot's altimeter   provides   a   servoed   counter   drum/pointer display  of  barometrically  corrected  pressure  altitude, derived from the air data computer system.  T3  F3 For proper operation, the 2 ampere  AIR DATA ENCODER circuit  breaker  located  in  the  Avionics  section  of  the right  sidewall  circuit  breaker  panel  must  be  set.    The altimeter is 26 Vac powered and is protected by the 1 ampere  PILOT  ALTM  circuit  breaker  also  located  on the  right  wall  panel.      R    For  proper  operation,  the three ampere  AIR DATA circuit breaker located in the Flight   Section   of   the   right   side   wall   circuit   breaker panel must be set.  The altimeter is 26 Vac powered and  is  protected  by  the  1-ampere  PILOT  VS  ALTM circuit breaker also located on the right wall panel. (1)   The servoed altimeter provides the following displays: 1.   Counter drum display of altitude, in 20 feet increments. 2.   Pointer    display    of    altitude    between 1000 feet levels in 20-foot graduations.