ARMED FWD ARMED AFT DISCH FWD CARGO FIRE AFT ARM DISCH Dump bottle Metered bottle Lower forward cargo compartment Discharge nozzle (8) Metered bottle (3) Filter/regulator Dump bottle (2) AFT in-line pressure switch FWD in-line pressure switch FWD cargo compartment (ref) Flow valves Identification plate Warning plate Discharge port Discharge assembly Squib Safety relief and fill port Handle (2) Mounting bracket (3) Pressure switch AFT and bulk cargo compartments (ref) Lavatory smoke detector Power indicator Alarm indicator Interrupt switch Self-test switch Sensor Alarm horn 17-17 Figure 17-22.  Lavatory smoke detector diagram.  Figure 17-21.  Cargo and baggage compartment extinguishing system.  Lavatory Smoke Detector System  automatically. The smoke detector is located in the ceiling  of the lavatory.  [Figure 17-22] Refer to  Figure 17-23.  The lavatory smoke detector is  powered by the 28-volt DC left/right main DC bus. If there  is smoke in the sensing chamber of the smoke detector, the  alarm LED (red) comes on. The timing circuit makes an  intermittent ground. The warning horn and lavatory call  light operate intermittently. The smoke detection circuit  makes a ground for the relay. The energized relay makes a  ground signal for the overhead electronics unit (OEU) in the  central monitoring systems (CMS). This interface gives these  indications: lavatory master call light flashes, cabin system  control panel (CSCP) and cabin area control panel (CACP)  pop-up window shows, and the lavatory call chime operates.  Push the lavatory call reset switch or the smoke detector  interrupt switch to cancel the smoke indications. If there is still  smoke in the lavatory, the alarm LED (red) stays on. All smoke  indications go away automatically when the smoke is gone.