FLC ACR MLG ACFT INADVERTENTLY OPERATED THE ACFT IN NON COMPLIANCE WITH AN ACFT MEL PROVISIONS.

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FLT DEN-SAT HAD BEEN PREVIOUSLY MEL'ED REGARDING THE SVC INTERPHONE CHIME IN THE COCKPIT. DURING THE FLT; OUT OF CURIOSITY; IT WAS DISCOVERED THE ORIGINAL MEL #1; WAS IN ERROR AND SHOULD HAVE RELATED TO MEL #2. ODDLY ENOUGH; THE INOP CHIME STILL COULD HAVE BEEN INTERPRETED FOR THE ORIGINAL WRITE-UP DUE TO POORLY WRITTEN MEL #1. FLT DECK TO CABIN; CABIN TO CABIN; CABIN TO FLT DECK INTERPHONE SYS MAY BE INOP PROVIDED ALTERNATE; NORMAL; AND EMER PROCS ARE ESTABLISHED AND USED AND THE PA SYS OPERATES NORMALLY. THIS SEEMED TO SUFFICE UNTIL WE MADE OURSELVES AWARE OF MEL #2. THIS MEL STILL UNDER SVC INTERPHONE SYS RELATES TO THE ALERTING SYS. IT READS THAT THE VISUAL SIGNAL MAY BE INOP IN THE COCKPIT SAYING NOTHING ABOUT THE CHIME. SO COMES THE CONFUSION. THE SYS ITSELF COULD BE INOP UNDER MEL #2 BUT A COMPONENT WITHIN THE SYS (I.E.; AN ALERTING CHIME) COULD NOT. ALL BEING SAID IT WAS CONCLUDED THAT THE CHIME COULD NOT BE WRITTEN OFF AS AN MEL AND WE NOTIFIED THE COMPANY UPON LNDG IN KSAT. THIS STARTED THEM TO RETHINKING THE PLACARD; EVENTUALLY GNDING THE ACFT UNTIL THE REPAIR WAS MADE; ENDING THE DISPUTE. SINCE I WAS PART OF THE FLC INTERPRETING THE MEL ON THE CONSERVATIVE SIDE; I FEEL POSSIBLY AT RISK FROM A POORLY WRITTEN ASSESSMENT OF THE COCKPIT CHIME DEALING WITH THE INTERPHONE.