WHILE IN THE PATTERN AT MTN; PLT OF C310 FEARS DC ADIZ VIOLATION DUE TO UNCERTAINLY REGARDING XPONDER OP.

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MARTIN ARPT IS WITHIN THE DCA ADIZ AND UNDER CURRENT REGS; REQUIRES SPECIAL PROCS WHICH INCLUDE USING ASSIGNED XPONDER CODE AND TALKING TO ATC. I WAS FLYING ONLY IN THE LCL TFC PATTERN AND THEREFORE WAS TALKING TO MARTIN TWR THE ENTIRE TIME. I WAS ALSO SQUAWKING THE CODE ASSIGNED BY MARTIN. THE INFO THAT I RECEIVED FROM BOTH FLT SVC AND MARTIN TWR WAS THAT WAS ALL I HAD TO DO TO BE LEGAL. ON ONE OF THE DOWNWIND LEGS MARTIN TWR ASKED IF MY XPONDER WAS ON. AT THAT TIME; I CHKED THE SWITCH WHICH WAS IN THE MODE C POS. I ALSO RECYCLED THE SWITCH; WHICH HAD BEEN ON. I THEN SAID SOMETHING APOLOGETIC TO THE TWR LIKE; 'SORRY; TRY IT NOW;' TO WHICH I DID NOT RECEIVE A RESPONSE. I THEREFORE ASSUMED THAT ALL WAS WORKING OK. I CONTINUED TO FLY IN THE PATTERN AND IN COM WITH MARTIN TWR FOR ABOUT ANOTHER HR. I NEVER HEARD ANYTHING ABOUT THE MATTER AGAIN. UPON MAKING THE FINAL LNDG APPROX 1 HR LATER AND SWITCHING TO GND CTL; I WAS INFORMED THAT SOMEONE IN ADIZ AT A PHONE NUMBER IN VA WANTED TO TALK TO ME ABOUT MY LACK OF XPONDER. AT THIS TIME I ASKED THE LCL CTLR IF HE HAD BEEN RECEIVING MY XPONDER AND HE INFORMED ME THAT HE HAD BEEN RECEIVING IT OK EXCEPT FOR THE BRIEF TIME WHEN HE ASKED ABOUT IT.