"Ron Natalie" wrote in message
m...
Actually, one of the connectors on the rack into which the
transponder is installed has a set of contacts that are encoded
with the code for that aircraft. *Any* transponder plugged into
that position has the info for that specific airframe. Same kind
of technique is used for CVR, FDR and several other boxes.

I'm not talking about the physical location of the code.

I'm talking about the assignment. When your aircraft is registered
in the FAA database it gets a Mode S code (whether you have a Mode
S transponder or not). You can change the N numbers or the owners,
etc... but the Mode S assignment stays with that aircraft in the database.

I'd hate to see any kind of misunderstanding here but I still think
my response was perfectly valid for the previous three lines:
" Removing the transponder from a plane probably requires the technician
to zero the Mode-S number in the transponder. Installing a transponder
requires the tech to lookup the Mode-S number based on the N-number."

JK (one of those technicians, retired)