Narrative:

An small transport was proceeding swbnd on J6 25 mi northeast of mrb VORTAC at FL220. An medium large transport was handed off to the sector per letter of agreement climbing to 17000' on a converging course. Unfortunately I transposed the altitude of the small transport on to the requested altitude of the medium large transport and climbed the medium large transport to FL220. Note, FL200 showed in the data block. After the aircraft's mode C indicated FL204, I told the medium large transport to descend to FL200. The aircraft was still climbing and was as high as FL216 before beginning his descent. The aircraft came within 4.25 mi and 400'.

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Original NASA ASRS Text

Title: MLG WAS ISSUED CLIMB TO AN ALT ALREADY OCCUPIED BY ANOTHER ACFT. LESS THAN STANDARD SEPARATION RESULTED.

Narrative: AN SMT WAS PROCEEDING SWBND ON J6 25 MI NE OF MRB VORTAC AT FL220. AN MLG WAS HANDED OFF TO THE SECTOR PER LETTER OF AGREEMENT CLBING TO 17000' ON A CONVERGING COURSE. UNFORTUNATELY I TRANSPOSED THE ALT OF THE SMT ON TO THE REQUESTED ALT OF THE MLG AND CLBED THE MLG TO FL220. NOTE, FL200 SHOWED IN THE DATA BLOCK. AFTER THE ACFT'S MODE C INDICATED FL204, I TOLD THE MLG TO DSND TO FL200. THE ACFT WAS STILL CLBING AND WAS AS HIGH AS FL216 BEFORE BEGINNING HIS DSCNT. THE ACFT CAME WITHIN 4.25 MI AND 400'.

Data retrieved from NASA's ASRS site as of August 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.