Finally things seemed to click. I spent more time with the G3X Touch, G5 and GNX 375 installation manuals. I think I understand all the RS-232 connections and settings. I've updated the wiring spreadsheet with RS-232 connections for the ACK ELT and the TBD CO Detector. I also checked most of the RS-232 connections I made yesterday. I should be able to complete both RS-232 and ARINC connections in the spreadsheet and send my plans to Garmin for confirmation.