AIRSPACE VIOLATION.

Narrative

MY STUDENT AND I WERE ON A XCOUNTRY; WHEN 30 MI OUT OF ATLANTIC CITY CLASS C AIRSPACE. MY STUDENT CONTACTED ATLANTIC CITY APCH. THE FREQ WAS VERY BUSY AND THE CTLR CAME BACK WITH OUR CALL SIGN AND TOLD US TO STAND-BY. SINCE WE HAD ESTABLISHED 2-WAY RADIO COM; WE PROCEEDED ON COURSE. AFTER A COUPLE OF MORE CALLS; THE CTLR GAVE US A XPONDER-CODE. HOWEVER THE FREQ REMAINED VERY BUSY; SO WHEN WE WERE ABOUT 10 MI FROM ACY; I CALLED THE CTLR WITH A REQUEST TO BEGIN OUR DSCNT. THE CTLR CAME BACK AND TOLD US THAT WE WERE LEAVING HIS AIRSPACE. HAVING THE ARPT IN SIGHT; I WAS NOT ABLE TO UNDERSTAND THIS STATEMENT; I CAME BACK AND TOLD HIM THAT WE WERE 10 MI N OF THE ARPT. AFTER A FEW SECONDS THE CTLR TOLD US HE WAS UNABLE TO HAND US OFF AND THAT WE SHOULD SQUAWK VFR AND TRY ATLANTIC CITY ON 134.25. I THOUGHT WE HAD BEEN ON THAT FREQ ALL ALONG AND THAT THE CTLR HAD BECOME CONFUSED BECAUSE IT WAS SO BUSY. I DIDN'T WANT TO BOTHER HIM ANY MORE SO WE SQUAWKED VFR AND LEFT HIS AIRSPACE. WE DID CONTINUE TO MONITOR THE FREQ HOWEVER; AND IT WAS THEN THAT I HEARD ANOTHER ACFT CALL MCGUIRE APCH. UPON EXAMINING THE RADIOS; I SAW THAT WE HAD THE FREQ FOR MCGUIRE APCH IN RADIO #1 AND THE FREQ FOR ATLANTIC CITY APCH IN RADIO #2. HOWEVER THE XMIT-SELECTOR WAS ON #1. INSTEAD OF TALKING TO ATLANTIC CITY APCH; WE HAD BEEN TALKING TO MCGUIRE THE WHOLE TIME AND UNFORTUNATELY THEY DID NOT CORRECT US; NOR DID WE REALIZE THE MISTAKE UNTIL WE HAD VIOLATED ATLANTIC CITY'S CLASS C AIRSPACE.