A B737-200 WAS DISPATCHED IN NON COMPLIANCE WITH THE CABIN TO COCKPIT CALL CHIME INOP AND DEFERRED IN CONFLICT WITH THE MEL.

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SHIP X ARRIVED ZZZ WITH AN INBOUND PIREP 'DOOR 1R (1L) INTERPHONE INOP. CANNOT CHIME CAPT.' THE TIME RESTRAINT FOR THE FLT CALLED FOR DEFERRAL. MEL 23-00-04A; FLT DECK TO CABIN; CABIN TO FLT DECK FUNCTIONS WAS USED FOR DEFERRAL AND THE ACFT WAS EVENTUALLY DISPATCHED. AFTER ENTERING THE LOG PAGE I WAS CONTACTED BY ZZZ1 MAINT COORD AND TOLD THAT THE CHIME SYS IS NOT COVERED BY THIS MEL AND IS NOT DEFERRABLE. THE WRITE-UP WAS SELF EXPLANATORY AND I DECIDED TO LOOK THE DEFERRAL UP USING THE SHIP'S MECHANICAL DISPATCH MANUAL. THE MEL WHICH SEEMED TO COVER THIS PROB DID NOT NEED DISPATCH APPROVAL. I MADE SURE THAT THE INTERPHONE FUNCTIONED BTWN THE FORWARD POS AND THE COCKPIT AND NOTED SUCH IN MY SIGNOFF. I WAS LATER CALLED OUT TO THE AIRPLANE FOR AN EXTERNAL PWR PROB. WHILE WORKING THE PROB I DECIDED TO CHK THE COCKPIT CALL BUTTON ONE LAST TIME AND IT DID; IN FACT; WORK NORMALLY. HOWEVER; BECAUSE THE AIRPLANE WAS ALREADY ON DELAY I DECIDED TO LEAVE THE DEFERRED ITEM AS IT WAS. THE CHIME SYS THAT WAS FAULTED IS A DIRECT FUNCTION OF THE INTERPHONE SYS; OR SO CLOSELY RELATED THAT IT IS EASILY MISTAKEN TO BE A FUNCTION. (YOU USE THE CHIME TO GET THE CREW'S ATTN; THEN YOU TALK TO THEM ON THE INTERPHONE.) THE MEL I USED DOES NOT MENTION THE CHIME AT ALL. UNLESS YOU HAD FIRST HAND EXPERIENCE IN WHAT I AM GOING THROUGH; YOU WOULD BE HARD PRESSED TO MAKE THE DISTINCTION. THE MEL SHOULD HAVE A SIMPLE NOTE STATING THAT INOP CHIMES ARE NOT COVERED BY THIS MEL.