PLT OF A CPR SEL SMA DID NOT HAVE TAXI OR TKOF CLRNC DUE TO NOT KNOWING THAT THE TWR WAS OPEN SINCE THE FSS BRIEFER ADVISED THAT THE TWR DID NOT OPEN UNTIL AFTER RPTR'S PROPOSED DEP. HOWEVER; HE DID ANNOUNCE HIS TAXI AND TKOF INTENTIONS OVER THE TWR FREQ; BUT HAD INADVERTENTLY PRESSED THE WRONG BUTTON FOR XMITTING.

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I DEPARTED FROM HUNTSVILLE ARPT ON AN IFR FLT TO TRI. TKOF WAS AT XX45. I HAD CONTACTED THE FSS FOR AN UPDATED WX BRIEFING BY PHONE AT APPROX XX15. I WAS INFORMED BY THE BRIEFER THAT THE HUNTSVILLE TWR AND APCH CTL WERE CLOSED UNTIL XC00. SINCE HSV HAD BEEN OPERATING 24 HRS A DAY FOR SOME PERIOD; I REQUESTED AND RECEIVED FROM THE BRIEFER INSTRUCTIONS ON HOW TO GET A CLRNC WHEN THE FACILITY WAS CLOSED. BASED ON THE INFO GIVEN BY THE FSS; I XMITTED MY DEP INTENTIONS ON THE TWR FREQ (127.6). AS I RECALL; I BROADCASTED TAXI AS WELL AS TKOF INTENTIONS. I DEPARTED ON RWY 18L. THERE WAS NO OTHER TFC IN THE AREA. SO I DID NOT KNOW IF I WAS XMITTING OR NOT. AFTER DEP; I CONTACTED ZME AND RECEIVED MY CLRNC. AT THIS TIME I REALIZED THAT I HAD DEPRESSED THE AUTOPLT DISABLE BUTTON INSTEAD OF THE PUSH-TO-TALK BUTTON. WHEN HSV APCH OPENED; ZME HANDED ME BACK TO HSV. AT THIS TIME; I WAS INFORMED THAT THE TWR WAS OPEN WHEN I DEPARTED; AND WOULD I CALL THE TWR AFTER LNDG. I BELIEVE THAT UNDER THE CIRCUMSTANCES; I ACTED SAFELY ON THE INFO I HAD AT THE TIME. I REGRET THIS HAPPENED.