Hi all,

I've improved the transponder instrument in order to have a generic transponder which work over network.
For complet information about changes you can take a look at the forum topic : http://www.flightgear.org/forums/viewtopic.php?f=75&t=19826
For this I've create a merge request : https://gitorious.org/fg/flightgear/merge_requests/1570

Also I've modified the KT76A in order to match the new transponder system : http://clemaez.fr/flightgear/KT76A.tar.gz 
The only changes needed on FGDATA is the <mode> tag in instrumentation XML. Also feel you free to add the KT76A in Aircraft/Instrument-3d

This is fully compatible with old FG version, properties (id-code and altitude) are simply ignored by old FG version.

For aircraft designer who want to use this new transponder, you just need to use the KT76A or implement your own with these specifications :
- /systems/electrical/outputs/transponder must be > 8.0
- /instrumentation/transponder/inputs/knob-mode is a INT with 0=OFF, 1=SBY, 2=ON, 3=ALT, 4=TST
- OFF = no power / no transmission
- SBY = standby, instrument is powered (e.g light animation) / no transmission
- ON = power ON / transmit id-code (sqwak)
- ALT = powerON / transmit id-code + altitude with 100ft precision for mode A&C and 10ft precision for mode S
- TST = test, same as ALT (test mode can't be generic because transponder model require different implementation, feel you free to suggest a generic test mode)
/instrumentation/transponder/inputs/digit[0-3] are INT from 0 to 7
/instrumentation/transponder/inputs/serviceable must be TRUE
- /instrumentation/transponder/inputs/mode is a STRING = A, C or S  defined by the instrumentation.xml file (look at the forum topic for example)

I'm ready to maintain this work and improve it when suggestion come to me.