Original Message

your hand if you didn't know ALT on the transponder needed to be selected for ATC to get your mode C.

It's fine, we have all done it....flown around with the supid thing set to the ON position and ATC starts bitching that they are not getting altitude....and then the Copilot sneak-aly switches the radio to ALT from ON and now it's working just fine for the rest of the day....