Sub-LAN Connection in open loop operation:
Why is the Sub-LAN Connection in open loop operation suggested?
Best Practice; It is recommended that if using the Sub-LAN in an open loop configuration that you jumper pin 1 to pin 4 and pin 2 to pin 5. This connects the primary and alternate ports.
This is important because if the controller fails to receive a response from a Sub-LAN device on the first attempt it will try the secondary attempt on the alternate port. Connecting these ports allows you to have three attempts at communicating with the device rather then just two.