Originally Posted by sbrower

Technically this post isn't right (I think). A transponder works on a fixed frequency, but you set a code. So it must be that they set the wrong code on the transponder, not the wrong frequency on the radio. And that is pretty dumb, because they tell you "Squak 7530" or something like that. However, even more likely is that in going to 7530, they went past 7600, which squawked once, and that is what set off the alarm.