ACR MLG CLRED CROSS MIZAR INTXN 12000 FT. CAPT ON COMPANY RADIO AND FO; PF; SET 11000 FT IN ERROR. WHEN CAPT BACK ON RADIO CTLR ADVISED RESTR APPLIED. ACFT DSNDED TO 11000 FT AND CTLR RECLRED FLT TO MAINTAIN 11000 FT AND CHANGE TO APCH CTL.

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DSNDING FROM FL240 THROUGH 16000 FT; 1 LEFT THE FO (PF) WITH ZOB ON THE #1 RADIO AND CALLED COMPANY AND RECEIVED ATIS ON THE #2 RADIO. IMMEDIATELY UPON RETURNING ATC EMPHASIZED THAT THE RESTR OVER MIZAR INTXN STILL APPLIED. THE FO DSCNT PROFILE EASILY MET THE 12000 FT RESTR. I ACKNOWLEDGED THAT WE KNEW THE RESTR APPLIED. I BELIEVE WE MAY HAVE BEEN DSNDING THROUGH 14000 FT OR 13000 FT WHEN ZOB MADE THAT XMISSION. APCHING 12000 FT I CALLED '1000 FT TO GO;' AS 11000 FT WAS SELECTED IN THE ALT ALERTER. ATC ASKED OUR ALT AND I ADVISED THAT WE WERE DSNDING TO 11000 FT. HE SAID THAT HE THOUGHT HE HAD CLRED US TO 12000 FT; BUT SAID THAT IT MAY HAVE BEEN HIS MISTAKE AND PLEASE ADVISE DTW APCH OF OUR ALT. HE THEN HANDED US OFF TO DTW APCH. CONTRIBUTING FACTORS: I LEFT ATC FREQ WITHIN 100 MI FROM THE DEST AND WAS UNABLE TO MONITOR THE ARR AND XING INSTRUCTIONS; THEREBY NOT BEING ABLE TO BACK UP THE PF. I DID NOT IMMEDIATELY QUESTION THE NONSTANDARD 11000 FT SELECTED IN THE ALT ALERTER. WHEN ATC CALLED CONCERNED ABOUT THE RESTR OVER MIZAR; I SHOULD HAVE INCLUDED THE ALT DSNDING TO; WITH MY RESPONSE. BY NOT HAVING ATIS AND COMPANY COMS COMPLETED PRIOR TO 100 NM FROM DEST; IT PUT AN ADDITIONAL WORKLOAD ON THE PF; AND ALSO LEFT ME UNAWARE OF OUR ATC CLRNC AND RESPONSIBILITIES.