A CESSNA PILOT DEPARTED TTN WITHOUT TKOF CLRNC AFTER MISINTERPRETING THE LOCAL CTLR'S INSTRUCTIONS.

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THE PROB AROSE BECAUSE OF A MISCOM ERROR ON MY PART (PIC). THE ARPT WHERE THE INCIDENT OCCURRED WAS ON RWY 24 AT TTN. THE CONTRIBUTING FACTORS THAT LED TO THE INCIDENT WERE A C152 WHO WAS TURNING FROM THE BASE LEG TO THE FINAL LEG OF THE TFC PATTERN AND AN ACFT WHICH LANDED PRIOR TO MY INITIAL RADIO CALL TO THE AIR TFC CTLR ON TTN TWR FREQ. AFTER MY STANDARD CHKLIST RUN-UP I CALLED THE AIR TFC CTLR ON THE TWR FREQ AND TOLD HIM THAT I WAS READY FOR MY DEP TO THE W. THE AIR TFC CTLR REPLIED AND TOLD ME THAT THERE WAS A CESSNA ON FINAL AND TO POS AND HOLD ON RWY 24. HOWEVER; I THOUGHT THAT THE TFC CTLR SAID THERE WAS TFC ON FINAL AND I WAS CLRED TO TAKE OFF. SO I READ BACK THE COMMAND AND SAID 'CESSNA XX DEP APPROVED.' I PROCEEDED ONTO THE RWY SET MY COMPASS TO THE RWY HDG AND STARTED TO BEGIN MY TKOF ROLL. THE WAY THE PROB WAS DISCOVERED ON MY PART WAS WHILE I BEGAN CLBING TO DEPART THE ARPT TO THE W THE AIR TFC CTLR CALLED ME ON THE RADIO AND TOLD ME THAT I WAS SUPPOSED TO BE IN A POS AND HOLD AND I WAS NOT CLRED TO TKOF. HE THEN TOLD ME THAT THERE WAS AN ACFT ON THE RWY THAT I DID NOT SEE WHEN I BEGAN MY TKOF ROLL; SO I DIPPED MY WING AND SAW THE ACFT ON TXWY A. THE ACFT WAS DOWN AND CLR; OFF OF THE RWY BUT JUST XING THE RWY HOLD SHORT LINE. THE AIR TFC CTLR THEN SAID TO PROCEED ON MY COURSE TO THE W SINCE IT WAS TOO LATE TO STOP ON THE RWY AND I WAS CLR OF ANY OTHER TFC ON THE FIELD. THE FACTORS AFFECTING MY QUALITY OF HUMAN PERFORMANCE WAS BEING TOO HASTY IN MY ACTIONS; TRYING TO MULTI-TASK BY FIXING MY COMPASS TO THE HDG OF THE RWY; AND NOT ASKING THE CTL TWR TO READ BACK HIS INSTRUCTIONS. MY PERCEPTION OF THE ENVIRONMENT WAS THAT THE ACFT WAS DOWN AND CLR OF RWY 24 AND WAS ALREADY ON TXWY A.