CONFLICT WITH CLBING TFC TCASII RA TO DSND.

Narrative

APCHING DXO FROM THE N ON THE POLAR 1 ARR. WE WERE WORKING WITH ZOB. AT 12000 FT AND AFTER PASSING POLAR AND ABOUT 30 MI N OF THE ARPT; I REQUESTED A LOWER ALT. ZOB DID NOT RESPOND TO US BUT WE COULD HEAR THE CTLR TALKING TO OTHER ACFT. AT ABOUT XA15 LCL OUR TCASII GAVE US A 'TA' AT OUR 1 O'CLOCK POS. WE WERE IMC AND HAD THE WX RADAR ON. THE RETURNS ON THE RADAR OBSCURED THE TFC RETURN AND THEIR ALT. AS I TURNED OFF THE RADAR AND REDUCED THE TCASII RANGE TO 10 MI I WAS THINKING THIS TFC IS PROBABLY WHY ZOB DID NOT GIVE US A LOWER ALT. WITH THE WX RETURNS OFF WE COULD SEE THE TFC AT OUR 1 O'CLOCK POS; 200 FT BELOW US AND CLBING APPROX 3 MI AWAY. AT THIS TIME WE RECEIVED AN RA TO DSND. THE IVSI DEMANDED APPROX 3000 FPM DSCNT WHICH WE ACCOMPLISHED. WE OBSERVED THE TFC ON THE SCREEN AT OUR ALT AND THEN ABOVE US. AT 11500 FT WE WERE GIVEN A 'MONITOR VERT SPD' AND AT 11300 FT A 'CLR OF CONFLICT.' WE LEVELED OFF AND AGAIN CONTACTED THE CTR. THE CTLR SAID HE HAD BEEN TRYING TO CONTACT US. WE TOLD HIM WE WERE AT 11300 FT AT WHICH TIME HE TURNED US OVER TO DETROIT APCH CTL. WE RPTED TO APCH CTL THAT WE WERE LEVEL AT 11300 FT (CLRNC WAS 12000 FT) BECAUSE OF A TCASII RA. WE WERE VERY CLOSE TO THE ARPT AT THIS TIME AND ASKED FOR ADDITIONAL VECTORS TO ALLOW US TO LOSE ALT. THE REST OF THE APCH AND LNDG WAS NORMAL.