Transponder is from a dual screen 5600 system that wouldn't fit in my current project. Was hoping to use parts of that system on this build, but sounds like the transponder should stay with that system. So if I go with an SV-ARINC-429, why do I need to swap out the RedBox? I though that was connected with the "compass" on the main EFIS connector. I can get a standalone transponder that does not need a serial connection, and if I go with the remote mount Val solution for NAV/COM, serial ports would be:
1) VPX
2) TruTrakAP
3) SL-30 (Val NAV and COM 2k)
4) AF-GPS

I was having difficulty finding in the manual how you wire the SV network into the system. Does this require a serial port as well? Sorry if these questions are novice.