"Mike Ferrer" wrote in message
...
Depends on the transponder. The Garmin GTX-330, for example, is software
programmable and swapping out transponder requires keyboard entry of the
mode S address by the technician. Not to mention recertification by a
certificated repair station...

Mike

Thanks for the info. Sometimes I assume too much from
my experience limited to 727 ... 767 & DC-10.

JK

"Jim Knoyle" wrote in message
...

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.