CAPT OF A JETSTREAM 4100 TOOK TAXI CLRNC BY LCL CTL TO CROSS RWY AND HOLD BY MISTAKE WHICH WAS MEANT FOR AN MD80 HOLDING AT ANOTHER RWY TXWY INTXN.

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INITIAL TAXI CLRNC: TAXI TXWY K; TXWY S; HOLD SHORT OF RWY 4L FOR RWY 9. WHILE HOLDING SHORT; I HEARD A CALL TO CROSS RWY 4L; MONITOR 119.1 ON THE OTHER SIDE; BUT THIS CALL WAS FOR THE ACR Y MD80 AHEAD AT TXWY E. I THOUGHT FO RESPONDED TO CTLR; BUT HE LATER SAID HE DIDN'T. I MUST HAVE HEARD THE ACR Y PLT RESPOND. I REPEATED THE CLRNC OUT LOUD THINKING IT WAS FOR US. FO DIDN'T CORRECT ME BECAUSE HE THOUGHT HE MISSED THE CALL AND THAT I WAS RESPONDING/XMITTING OVER THE RADIO. IN FACT; I WAS SIMPLY REPEATING A CLRNC THAT I THOUGHT HE HAD RESPONDED TO. I LOOKED BOTH WAYS AND THE RWY AND FINAL WERE CLR. I THEN CROSSED ILLEGALLY. CONTRIBUTING FACTORS: I WAS TIRED FROM REDUCED REST OVERNIGHT. ALTHOUGH I SHOULD NOT FLY TIRED; THE REALITY IS WITH THE FARS WRITTEN AS IS; MANY PLTS FLY TIRED (OR WE'D NEVER FLY) AND THIS WILL NOT CHANGE UNTIL THE FAA CHANGES THE FARS. A CERTAIN AMOUNT OF MY OWN COMPLACENCY IS ALSO TO BLAME. (I WAS TOLD TO CONTACT THE TWR AFTER THE FLT; AND BY THAT TIME I HAD FIGURED OUT WHAT HAD HAPPENED REGARDING THE MISCOM IN THE COCKPIT. NO ACFT CONFLICT AROSE FROM THIS INCURSION.)