TFC CONFLICT BETWEEN 2 LCL CTLRS AT PIT.

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I WAS WORKING THE LC1 (LCL CTL 1; S SIDE OF THE PIT ARPT) POS RESPONSIBLE FOR SBOUND DEPS AND LNDG TFC. ACFT X CALLED READY FOR DEP FROM RWY 28L AT INTXN P. I SCANNED THE RWY FOR TFC AND ISSUED A TKOF CLRNC AND ON INITIAL HDG OF 200 DEGS. AS THE ACFT LIFTED I SAW A C208; ACFT Y SBOUND OVER THE TERMINAL. I ISSUED TFC TO THE SF34 AND A TURN TO THE R. THE CARAVAN MADE A TURN TO AVOID THE SF34 AT THE SAME TIME. AFTER THEY PASSED I ISSUED AN ON COURSE HEADING AND SWITCHED THE SF34 TO DEP PRIOR TO LEAVING THE FREQ. HE STATED 'THAT WAS CLOSE.' THE OTHER LCL CTLR BELIEVED HE HAD GOTTEN APPROVAL FROM ME TO RELEASE HIS DEP BUT THE COORD WAS NOT DONE ON THE IN-HOUSE LANDLINE AND I NEVER HEARD OR ACKNOWLEDGED HIS REQUEST. WHEN I OBSERVED THE CARAVAN OVER THE TERMINAL SBOUND IT WAS A COMPLETE SHOCK TO ME. SUPPLEMENTAL INFO FROM ACN 556995: COORDINATED WITH LC1 FOR A SBOUND (A300) FDX DEP OVER 'BURGS' AFTER ARR FOR RWY 28R. VERBALLY COORDINATE WITH LC1 FOR A SBOUND (C208) OVER GRV. RECEIVED WHAT I BELIEVED TO BE AN ACKNOWLEDGEMENT FROM LC1. PRIOR TO THE C208 TURNING S; I SCANNED RWY 28L AND DIDN'T SEE THE SF34 DEPARTING. I NORMALLY DO THIS AS A SECONDARY CHK. I THEN XFERRED COMS TO DEP. SHORTLY AFTER; I NOTICED AND HEARD LC1 TURNING AN ACFT TO AVOID THE C208. BOTH ACFT TURNED TO AVOID EACH OTHER. IN THE FUTURE I WILL ALWAYS USE LANDLINES TO COORDINATE DEPS WITH THE OTHER LCL. SUPPLEMENTAL INFO FROM ACN 557133: AT XA45 WAS CLRED FOR TKOF ON RWY 28R AT PIT WITH INSTRUCTIONS TO TURN L TO A HEADING OF 190 DEGS. AT 1700 FT MSL; I BEGAN MY L TURN TO 190 DEGS AND WAS HANDED OFF TO DEP CTL. I CHKED IN AT '1900 FT MSL FOR 4000 FT MSL IN MY TURN TO 190 DEGS.' CTLR; SAID 'RADAR CONTACT; CLB AND MAINTAIN 5000 FT.' I ACKNOWLEDGED 5000 FT AND AS I ROLLED OUT OF MY TURN ON 190 DEGS I SAW THE COMMUTER AT 10 O'CLOCK POS AND BELOW ME CLBING THROUGH MY FLT PATH. I BEGAN A R TURN TO DECREASE THE CLOSURE RATE AND HE BEGAN A R TURN TO PASS BEHIND ME. ESTIMATED DISTANCE WAS WITHIN 500 FT AT THE SAME ALT. CAUSE: COMMUTER WAS CLRED FOR TKOF ON RWY 28L AS I BEGAN MY L TURN TO 190 DEGS WHICH TOOK ME ACROSS THE DEP PATH OF RWY 28L. PREVENTION: BETTER COM BTWN THE 2 SEPARATE TWR CTLRS (128.3 FOR RWY 28R AND 119.1 FOR RWY 28L) OR WHOEVER COORDINATES THE DEPS.