TM 10-6640-238-13 2-15 g. Vacuum System Controls and Indicators.  Figure 2-8 and Table 2-8 list the controls and indicators for the vacuum system. Table 2-8.  Vacuum System Controls and Indicators Index Number Control or Indicator Function 1 Vacuum Pump START/STOP Controller Starts and stops vacuum pump for system operation. 2 Vacuum System Oil Overflow Drainage Valve Provides oil overflow drainage. 3 Vacuum System Isolation Valve Provides system isolation  (Removes vacuum from laboratory lines). 4 Vacuum System Service Valves Provides system service access to vacuum system.  Two are located on roadside wall and one in fume hood. 5 Vacuum Gauge Isolation Valve Provides isolation of gauge to system. 6 Vacuum/Pressure Gauge Indicates system vacuum in inches of mercury (HG).