MD80 CAPT INDICATED THAT A LAV SMOKE DETECTOR HAD ACTIVATED. COMMUNICATION WITH THE FLT ATTENDANTS WAS NOT POSSIBLE BECAUSE THE CABIN CHIMES BECAME INOP WHEN THIS WARNING OCCURRED.

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ON APCH; AN MD80; AFT R LAVATORY SMOKE DETECTOR ACTIVATED: 4 SINGLE CHIMES IN THE CABIN FOLLOWED BY SILENCE; LAVATORY CALL LIGHT ON; AND 'LAVATORY SMOKE DETECTOR' ANNUNCIATED. TRIED TO CHIME CABIN; BUT COCKPIT-TO-CABIN CHIME DID NOT WORK. CABIN-TO-CABIN CHIME WAS ALSO INOP; AND CABIN-TO-COCKPIT CHIME WAS INOP. ALL CHIMES REMAINED INOP UNTIL THE SMOKE DETECTOR WARNING STOPPED. AFTER THAT; ALL CHIMES NORMAL. THE SMOKE DETECTOR TURNED OUT TO BE A FALSE ALARM; BUT THE PERFORMANCE OF THE CHIMES DURING A POTENTIAL EMER IS OF CONCERN. I WROTE UP THE SMOKE DETECTOR AND THE CHIMES AS SEPARATE ITEMS IN THE LOGBOOK. LINE MAINT PERSONNEL SIGNED OFF THE CHIME AS PART OF THE PLACARDED LAVATORY SMOKE DETECTOR. WHEN THE SMOKE DETECTOR WAS REPAIRED; THE CHIME WRITE-UP FELL THROUGH THE CRACKS. I FOLLOWED THIS WRITE-UP AND CONTACTED MAINT TO FIND OUT IF INOP CHIMES ARE A NORMAL PART OF A SMOKE DETECTOR EVENT. MECH CHKED WITH ENGINEERING; WHO SAID THIS WAS NOT NORMAL OP. MECH ISSUED AN INFO ITEM ON THE INCIDENT AIRPLANE; REQUESTING LINE MAINT TO SET A SMOKE DETECTOR IN 'TEST;' AND TEST THE CHIMES. LINE MAINT RPTED THAT THE COCKPIT-TO-CABIN CHIME WAS INOP IN THAT MODE; AND CLRED THIS ITEM. I CALLED ENGINEERING AND SPOKE WITH ANOTHER TECHNICIAN; WHO SAID THAT INOP CHIMES WERE NORMAL WITH THE SMOKE DETECTOR ACTIVATED; SO WE HAVE 1 'NORMAL' AND 1 'BROKEN.' 3 RECOMMENDATIONS: 1) FIND OUT IF INOP CHIMES ARE NORMAL IN THESE MD80'S WITH A SMOKE DETECTOR ACTIVATED. 2) IF NORMAL; DO MORE TO EDUCATE PLTS AND FLT ATTENDANTS ABOUT THAT. MY INFORMAL POLL FOUND THAT ZERO PERCENT OF PLTS AND FLT ATTENDANTS KNEW ABOUT THE 4 SINGLE DINGS FOLLOWED BY SILENCE AND INOP CHIMES. 3) IF INOP CHIMES ARE NOT NORMAL; INSPECT EACH MD80 AND REPAIR AS NECESSARY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT THE FOUR CABIN CHIMES WERE HEARD WHEN THE 'LAV SMOKE DETECTOR' ANNUNCIATION APPEARED. THIS SIGNAL PREVENTED THE CABIN CHIME SYSTEM FROM WORKING AS LONG AS THIS ANNUNCIATION WAS VISIBLE. WHEN THE ANNUNCIATION DISAPPEARED; THE CHIMES WORKED NORMALLY. MAINT WAS UNABLE TO VERIFY IF THE CHIMES WERE AN ANOMALY OR IF THE SYSTEM WAS DESIGNED TO OPERATE THIS WAY.