FLEW TRIP WITH ACI ON JUMP SEAT WITH ACFT SYSTEM INOP IN VIOLATION OF MINIMUM EQUIPMENT LIST.

Narrative

OUR FLT WAS DELAYED IN DEPARTING BECAUSE THE STATION AGENTS DECIDED TO ADD SEVERAL PAX FROM OTHER FLT TO OUR FLT. ONE OF THE REACCOMODATED PAX WAS AN FAA INSPECTOR WHO HAD INTENDED TO ROUTE CHK ANOTHER CREW; BUT DECIDED ON US AS THE OTHER FLT HAD NOT ARRIVED YET. THERE WAS A PROB WITH HIS PAPERWORK AS THE STATION PERSONNEL HAD NOT ISSUED HIM A COMPANY COCKPIT PASS; THEY HAD ONLY REVIEWED HIS FAA REQUEST FOR TRANSPORTATION FORM. IT TOOK US SEVERAL MINS TO STRAIGHTEN THIS OUT WHILE WE WERE ALSO DEALING WITH FUEL ORDERS; LOAD MANIFESTS AND OTHER PAPERWORK. AS THE INSPECTOR WAS BEING SEATED; HE ADVISED ME THAT THE OBSERVERS AUDIO PANEL WAS INOP. I TOOK A MIN TO CONFIRM THE PANEL WAS INDEED INOP; SOLVED THE PROB BY TURNING UP THE COCKPIT SPEAKERS SO HE COULD HEAR; AND PROCEEDED TO OPERATE THE FLT AS NORMAL. I FAILED TO CONSULT THE MEL CONCERNING ANY RESTRICTIONS OR PROCS REGARDING THE OBSERVER'S AUDIO PANEL. AS THE INSPECTOR POINTED OUT TO ME AT THE CONCLUSION OF THE FLT; THE MEL DOES NOT MENTION AUDIO PANELS AT ALL; HENCE ALL MUST BE INSTALLED AND OPERATIVE. THE CONDITION WAS RECORDED AND CORRECTED BEFORE THE ACFT DEPARTED ON ITS NEXT FLT.