ACR X TCASII RA WITH ACR Y CLB THROUGH OCCUPIED ALT. EVASIVE ACTION CLB. POSSIBLE LTSS.

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FREQ CONGESTION WAS GETTING HVY. VFR ACTIVITY WAS INCREASING. WITHOUT REGARD FOR FREQ DISCIPLINE VFR WERE HELPING A LOST VFR -- WHO WAS UNABLE TO HEAR ME. LOW STRATUM WAS BROKEN OFF A FEW MINS BEFORE TCASII EVENT OCCURRED. SIMILAR SOUNDING CALL SIGNS AND FREQ PROBS AND A STRONG IRRITANT SMELL WHICH WAS PERMEATING THE ROOM WERE ALSO FACTORS. THE SMELL WAS STRONG ENOUGH TO CAUSE A HEADACHE AND EYE IRRITATION. THE SYS WAS DARC HOST ONLY WHICH INCREASED THE WORKLOAD. ACR X WAS WBOUND AT FL280 IN CRUISE FLT. ACR Y CAME OFF OF PHOENIX ON 1 OF 2 AIT (AUTOMATED INFO TRANSFERS) THAT ARE AVAILABLE FOR THIS TYPE DEP. Y WAS IN A CLB TO FL290 FROM PREVIOUS SECTOR. A FEW MINS LATER ANOTHER DEP FROM PHOENIX CAME OFF CLBING TO FL230; THE OTHER OF THE TWO DEP AIT AVAILABLE. THIS ACFT WAS CLBED TO FL270 FOR X. AFTER THE TFC SEARCH WAS ACCOMPLISHED FOR THIS ACFT IT WAS REALIZED AND NOTICED THAT Y WAS CLBING TO FL290 OUT OF FL268. Y WAS ISSUED AN IMMEDIATE DSND TO FL270. Y READBACK 'DID YOU SAY FL240.' THE CLRNC WAS REISSUED. X HAD RECEIVED A TCASII RA AND HAD STARTED TO CLB WITH Y IN AN IMMEDIATE DSCNT AND X IN A CLB OF 2000 FPM FOR A 1000 FT SEPARATION WAS NEVER LOST. AFTER 5 3/4 MI DIMINISHED AN ALT OF FL287 FOR X AND AN ALT OF FL277 WAS ATTAINED BY Y. X LEVELED AT FL270 AND Y RETURNED TO FL280 AFTER PASSING. THE RADAR AND RADAR ASSOCIATE POS WERE STAFFED. ONE OTHER SECTOR WAS COMBINED WITH THE SECTOR THE INCIDENT OCCURRED. WITH 22-25 AIRPLANES TFC WAS MODERATE TO HVY AND VERY COMPLEX GIVEN THE STATE OF THE COMPUTER SYS; THE ENVIRONMENT AND WORKLOAD. SUPPLEMENTAL INFO FROM ACN 306333: Y CLBED TO FL277 BEFORE DSNDING BACK TO FL270. TCASII SAID TO CLB; I DID SO TO FL290 LETTING ATC KNOW AT THE SAME TIME I WAS CLBING TO CLR TFC. NO RESPONSE FROM ATC UNTIL I LEVELED AT FL290. THIS HAPPENED 35 MI NW SSO VOR. WAS INSTRUCTED TO CALL ATC. DID SO AND FOUND OUT IT WAS THEIR FAULT WITH LOW LEVEL ATC.