STUCK MICROPHONE EFFECT CREATED ON ACR BY ACFT EQUIP MALFUNCTION WHEN JACK BOX SELECTOR BECOMES A PROBLEM.

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GIVEN DSCNT TO CROSS HULEN AT 11000; ALREADY ASSIGNED 250 KTS. AFTER A LONG PERIOD OF NO XMISSIONS FROM FT WORTH CTR; THE FO CALLED TO SEE IF HE WAS STILL ON FREQ. THEY RESPONDED THAT WE HAD HAD A STUCK MICROPHONE FOR QUITE A WHILE. I SELECTED 'INTERCOM' AND TOLD THE FO THAT HE WOULD BE DOING ALL RAPID CALLS FOR THE REST OF THE FLT. AFTER LNDG OUR COMPANY TWR ASKED US TO CALL FT WORTH CTR. THE MATTER WAS DISCUSSED; WITH THE CTLR NOTING THAT NO TFC CONFLICT(S) OCCURRED; BUT THAT ONE 'MIGHT' HAVE. FOR WHAT IT'S WORTH; WHEN YOU ARE THE ONE WITH THE 'STUCK MICROPHONE' YOU DON'T USUALLY KNOW IT. AS FAR AS HOW LONG A TIME IS 'TOO LONG' FOR NO XMISSIONS RECEIVED FROM THE CTLING AGENCY TO BE A 'CLUE' THAT YOU HAVE A PROB; IT'S A 'JUDGEMENT CALL'. ALSO; WE HAD AN ATC JUMPSEAT RIDER ON BOARD (WHAT IRONY!) WHOSE 'JOB' WAS TO RIDE AROUND LISTENING TO ATC CTLR'S PERFORMANCE. PERHAPS; WITHOUT A PERSON ON THE JUMPSEAT PROVIDING AN ADDITIONAL SOURCE OF 'CONVERSATION' (WE WERE STILL ABOVE 10000 FT); THE 2 PLTS WOULD HAVE NOTICED THE 'GAP' IN COMS A BIT EARLIER. ON THE OTHER HAND; I RECOGNIZE THE NEED FOR HIM TO PERIODICALLY RIDE ALONG TO CHK OUT THE ATC SYS.