28V DC Left/right main DC LAV smoke detect L/R P110/210 PWR MGMT panel Smoke Sensing chamber Smoke detect circuit Lavatory smoke detector Lavatory Timing circuit Horn Call light Reset Power on (green) Alarm (red) Smoke Test Interrupt alarm CMS Master call light (amber) Test Smoke Indications • Chime • CACP/CSCP • Pop-up window Pulsed ground if smoke detected A Test Interrupt LAV call light/ reset switch 28V AC 180° 200° 230° Temperature Indicator Strip 250° 18 0° 20 0° 23 0° Temper $^{ature I}$ndi c $^{ato}$r $_{Str}$ i p 25 0° Fire extinguisher bottle Figure 17-23.  Lavatory smoke detector diagram. Figure 17-24.  Lavatory fire extinguishing bottle.  Lavatory Fire Extinguisher System Fire Detection System Maintenance 17-18 Note: These procedures are examples and should not be used  to replace the applicable manufacturer’s instructions. Fire detector sensing elements are located in many high- activity areas around aircraft engines. Their location, together  with their small size, increases the chance of damage to the  sensing elements during maintenance. General maintenance  of a fire detection system typically includes the inspection and  servicing of damaged sections, containment of loose material  that could short detector terminals, correcting connection  joints and shielding, and replacement of damaged sensing  elements. An inspection and maintenance program for all  types of continuous-loop systems should include the following  visual checks. The lavatory compartment is outfitted with a fire extinguisher  bottle to extinguish fires in the waste compartment. The fire  extinguisher is a bottle with two nozzles. The bottle contains  pressurized Halon 1301 or equivalent fire extinguishing agent.  When the temperature in the waste compartment reaches  approximately 170 °F, the solder that seals the nozzles melt  and the Halon is discharged. Weighing the bottle is often  the only way to determine if the bottle is empty or full.  [Figure 17-24] Sensing elements of a continuous-loop system should be  inspected for the following: 1.  Cracked or broken sections caused by crushing or  squeezing between inspection plates, cowl panels, or  engine components. 2.  Abrasion caused by rubbing of the element on cowling,  accessories, or structural members.