ZOB controller experienced loss of separation at FL220.

Attributes
ACN	590610
Time
Date	200308
Day	Fri
Local Time Of Day	1201 To 1800
Place
State Reference	OH
Altitude	msl single value : 22000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	general aviation : personal
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	Jetstream 32
Operating Under FAR Part	Part 135
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 11
ASRS Report	590610
Person 2
Affiliation	other
Function	flight crew : single pilot
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 24000 vertical : 800
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft X, a T/J320/6, inbound to cle at FL240 and a BE20/G, aircraft Y was nwbound direct msn. I intended to descend aircraft X to FL230, but misspoke and said FL210. When aircraft X was through FL227 I questioned the clearance and turned aircraft X 25 degrees right and descended aircraft X to FL210 uedp activated.

Original NASA ASRS Text

Title: ZOB CTLR EXPERIENCED LOSS OF SEPARATION AT FL220.

Narrative: ACFT X, A T/J320/6, INBOUND TO CLE AT FL240 AND A BE20/G, ACFT Y WAS NWBOUND DIRECT MSN. I INTENDED TO DSND ACFT X TO FL230, BUT MISSPOKE AND SAID FL210. WHEN ACFT X WAS THROUGH FL227 I QUESTIONED THE CLRNC AND TURNED ACFT X 25 DEGS R AND DSNDED ACFT X TO FL210 UEDP ACTIVATED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.