B737-200 CAPT DID NOT SET QNE AT THE TRANSITION LEVEL IN ZID CLASS A AIRSPACE.

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WE WERE FLYING A REVENUE PAX FLT; ACR X; FLT ABCD FROM CVG TO PHL. THE FO WAS FLYING AND HAD BEEN CLRED TO CLB FROM 15000 FT TO FL230. AFTER THE CLB WAS INITIATED; BUT BEFORE REACHING FL180 (PCA); I GOT DISTR WITH A FREQ CHANGE; A WARNING FROM THE CTLR THAT ACR X EFGH WAS ALSO OPERATING ON FREQ; A TURN DIRECT TO JOHNSTOWN VOR; AND A CALL FROM THE BACK. AFTER RESPONDING TO THE CALLS; I LOOKED DOWN AT MY CHART FOR THE JST FREQ; DIALED IT IN; SWITCHED FREQS AND CHKED IN WITH THE NEW CTLR. WHILE DOING SO; I LOOKED AT MY ALTIMETER AND SAID 'GOOD MORNING; FLT ABCD OUT OF FL230 FOR...' (AND LOOKED TO SEE THE ALT WINDOW ON THE MCP WAS FL230!) AND REALIZED MY ALTIMETER WAS AT APPROX FL232+ WITH AN ALTIMETER SETTING OF 30.47. THE FO WAS LEVEL AT FL230 AND HSI ALTIMETER WAS SET ON 29.92. SO; WHILE WE WERE LEVEL AT OUR ASSIGNED ALT OF FL230; MY ALTIMETER MAY HAVE INDICATED HIGHER. I DIDN'T HEAR HIS '29.92' CALL WITH ALL THE NOISE AND DISTRS; AND GOT OVERLOADED WORRYING ABOUT FLT EFGH ON THE FREQ. NO COMMENT FROM THE CTLR. REST OF FLT UNEVENTFUL.