Sorry if this has been asked before. I'm using an EX R3/RSW as a secondary (backup) receiver for my DS-24 in double path. Which port on the R3/RSW receiver do I plug into? My primary receiver is an REX10A with E1 set to EXBUS/Backup and failsafe enabled. The R3/RSW serial link is set to EXBUS and failsafe is disabled. When I plug an extension from the E1 port on the REX10A primary receiver to port 1, 2 or 3 on the R3/RSW it doesn't work when I disable the primary receiver. When I connect E1 on the primary receiver to port 4 (EXT) on the R3/RSW it works. I thought I needed to use a control port on the R3/RSW. If so, then maybe I'm not binding the primary and secondary receivers properly or in the right order. Any suggestions for connection and settings will be greatly appreciated.