CAUTION WARNING AIMS DISCH GLYPH<0>L GLYPH<0>E GLYPH<0>FGLYPH<0>T DISCH GLYPH<0>R GLYPH<0>IGLYPH<0>G GLYPH<0>H GLYPH<0>T Engine fire detectors Loop 1 Master caution light (2) Master warning light (2) P10 control stand L FUEL CONTROL R ENGINE BOTTLE 1 DISCHARGE  ENGINE BOTTLE 2 DISCHARGE FIRE/ OVERHEAT TEST RUN CUTOFF L&R Systems ARINC 629 buses P8 engine fire panel Speaker (2) Loop 2 Fire detection card - ENG Pressure switch cargo  fire/engine control panel Figure 9-20.  Engine fire detection system. the right sidewall lining of the forward cargo compartment,  aft of the cargo door.  [Figure 9-22] The two engine fire extinguishing bottles are identical. Each  bottle has these following components: The bottles contain Halon fire extinguishing agent pressurized  with nitrogen. If the pressure in the bottle becomes too high,  the safety relief and fill port opens so the bottle does not  explode. The discharge assembly has an explosive squib. An  electric current from the fire extinguishing circuit fires the  squib. This releases the Halon through the discharge port.  The pressure switch gives flight deck indications when bottle  pressure decreases. The switch monitors the pressure inside  the bottle and is normally open. When the pressure decreases  because of a leak or bottle discharge, the switch closes an  indicating circuit. The squib is installed in the discharge assembly at the bottom  of the fire container. A fire container has two squibs, one for  each engine. The squib is an electrically operated explosive  device. When the squib is activated, it fires a slug through  the breakable disk, and nitrogen pressure inside the bottle  pushes the Halon through the discharge port. The squib fires  when the fire switch is pulled and turned to the DISCH 1 or  DISCH 2 position.  [Figure 9-22]  The engine fire panel is in the flight deck on the P8 aisle stand.  The engine fire panel has a fire switch for each engine and a  discharge light for each fire bottle.  [Figure 9-26] The engine fire switch has four functions:  The fire switch assembly incorporates a solenoid that locks  the fire switch so that the flight crew cannot pull it accidently.  •  A safety relief and fill port •  A handle for removal and installation •  A pressure switch •  Two discharge assemblies •  An identification plate •  Four mounting lugs  [Figures 9-23, 9-24, 9-25] •  Gives an indication of an engine fire •  Stops the engine •  Isolates the engine from the airplane systems Squib Engine Fire Switches 9-15 •  Controls the engine fire extinguishing system