What I was wondering was if the transponder could be set to respond to a "request for information" from the tower, so that the pilot did not have to squawk it manually. I realize that the squawk won't identify friend from foe, but it would give the tower information about the aircraft without requiring pilot cooperation. Done correctly, it could tell the tower much, much more -- including the status of onboard personnel. A certain code entered into the sender could indicate to the tower that the plane is in a silent "alarm" mode, for example.
I'm no aeronautical electronics wiz, but it seems to me that a microprocessor could be programmed to respond with some minimal datastream if prompted by a poll from the ground on a certain frequency.
I’m guessing you haven’t flown in quite some time (based on your use of the term ‘’ARSA’’ - which was replaced with ‘’Class C airspace’’ well over a decade ago) but just to bring your comments up to date:
‘’Squawk’’ refers to setting your transponder to the code ATC assigned you. ‘’Ident’’ is the button you push at ATC’s request to make your aircraft light up on their rada scope.
If you’ll think back to your initial training, there are discrete transponder codes for various emergencies. 7700 indicates an emergency, 7600 indicates radio failure, and 7500 is a hijacking. Any pilot will learn these codes in the course of their initial training. Of course, if a hijacker were in control, he would be able to set any transponder code he wanted.
On a side note, unless you got in big trouble with the FAA at some point, you’re still a private pilot, just way out of currency.