TM 5-6115-593-12 TO 35C2-3-463-1 the following engine operating conditions: oil pressure, oil temperature,   water   temperature   and fuel  level.    Transmitters  MT1  through MT4  which  are  connected  to  gauges M1  through  M4,  are  actually  variable resistors whose resistance changes as a   function   of   the   parameter   being monitored.  Once the engine starts all of these circuits are activated through normally   open   contacts   3   and   4   of relay   K1.      Meter   M5   is   an   elapsed time  meter  which  is  energized  by  K1 contacts    only    when    the    engine    is running. (3) Fuel Transfer.  Prolonged operation of the  engine  generator  set  is  obtained by   the   use   of   additional   fuel   tanks. The  transfer  of  fuel  from  these  tanks to the day tank is controlled automatically   by   fuel   level   switches FL1  and  FL2.    FL2  senses  when  day tank  fuel  falls  below  a  certain  level and    closes    to    energize    relay    K20 through     FUEL     PUMP     AUTO-OFF switch  S9  and  high-level  switch  FL1. With  K20  energized,  motor  B1  starts pumping  fuel  to  the  day  tank.    When full,    FL1    opens,    deenergizing    K20 which  subsequently  stops  motor  B1. FUEL    PUMP    indicator    lamp    DS1 connected  across  B1,  lights  anytime fuel is being pumped. (4) Battle Short.  During battle conditions, the  requirement  of  continued  engine operation   may   override   the   need   to protect  the  engine.  BATTLE  SHORT switch  S7  when  set  to  ON,  energizes selfholding relay K50. Closed contacts  3  and  4  of  K50  bypass  the fault-sensing contacts of low fuel relay K8, water temperature switch WT1, oil temperature  switch  OT1,  oil  pressure switch   OP1,   and   overvoltage   relay K32. k. Miscellaneous. The following subparagraphs   briefly   describe   those   DC circuits     not     directly     related     to     engine operation: (1) BATTERY  CHRG  AMPS  meter  M21 monitors  battery  charging  current.    It is connected in series with the battery charger. (2) BATTERY CHRG VOLTS meters M20 monitors DC electrical system voltage. (3) The   digital   CLOCK   M111   indicates daily    time.        Switch    S52    (50    Hz) enables clock operation at either 50 or 60 Hertz. (4) The   panel   lights   are   controlled   by PANEL LT SW S11. (5) 24V DC CONTROL CIRCUIT BREAKER CB1 controls the application   of   24V   DC   to   the   DC Electrical Control System and may be used  to  shut  down  the  engine  during an emergency. (6) OPERATION-MAINTENANCE LOCKOUT   switch   S2   prevents   the engine    from    being    started    during maintenance.  It may also be used for emergency shut down. 1-15.  AC POWER GENERATION AND CONTROL SYSTEM.  (See FO-2.) a. Introduction.      The   purpose   of   the   engine generator   set   is   to   produce   an   electrical output.    To  accomplish  this  end,  an  AC  3- phase,  brushless-type  generator  is  directly coupled to the diesel engine.  The AC power generator  and  control  system  monitors  and controls  the  generator  set  to  ensure  that  a constant    output    in    terms    of    amplitude, phase,  and  frequency  is  maintained  under all permissible load conditions and modes of operation.  The following paragraphs explain and  describe  the  various  functions  of  this control system. 1-26