ACR ALT DEV RESPONDING TO TCASII RA.

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OVER THE BUCKS INTXN (LRP 104/26); LEVEL 8000 FT WE RECEIVED A TCAS TFC ADVISORY. THE CAPT ATTEMPTED TO OBTAIN VISUAL CONTACT WITH THE TFC. ATC ADVISED US OF THE TFC AND ASKED US IF WE WISHED TO TURN TO AVOID IT. SIMULTANEOUSLY; THE CAPT STATED 'YES; WE'LL TAKE A TURN' AND THE TCAS ISSUED A RESOLUTION ADVISORY. AS I RELAYED THIS REQUEST TO ATC; THE CAPT DISCONNECTED THE AUTOPLT AND STARTED A TURN. THE RESOLUTION ADVISORY VSI DISPLAYED A SLIGHT CLB INDICATION; AND THE AURAL ADVISORY STATED 'CLB; CLB.' THE CAPT; WHILE STILL TRYING TO OBTAIN VISUAL CONTACT STARTED TO DSND IN THE TURN. I XCHKED HIS VSI AGAINST MINE TO INSURE THAT IT INDICATED THE SAME INFO THAT MINE DISPLAYED. I IMMEDIATELY TOLD HIM TO 'CLB INTO THE GREEN; YOU'RE DSNDING.' HE ARRESTED HIS DSCNT AT 7700 FT AND OVERSHOT TO 8200 FT AND STABILIZED AT 8000 FT. WE DISCUSSED THE SITUATION ON LNDG. IT WAS CLR THAT THE CAPT WAS FOCUSED ON ATTAINING VISUAL CONTACT. HE NEVER SAW THE CLB INDICATION IN THE VSI AND THE AURAL CLB COMMAND DID NOT IMPACT HIS DECISION PROCESS. THIS WAS HIS FIRST RESOLUTION ADVISORY. COMMENTS: TCAS RESOLUTION ADVISORIES NEED TO BE INCLUDED IN SIMILAR PROFICIENCY CHKS.