The LSNG connects to both the BS-420 panel and the Local Safety Network from ports on the Dual Universal Safety Carrier that houses the LSNG. The carrier must be connected to the panel's two devices using separate network segments. There should be no common switches or routers between them. While these are not redundant connections, they are dual simplex and must be independent.
The network routing is critical to achieve the SIL2 rating.
The figure shows the Dual Universal Carrier with Ethernet Isolation Ports installed. The upper ports, labeled Modbus Port 1 and Modbus Port 2, connect to the panel. The two lower ports, labeled Primary LSN Port and Secondary LSN Port, are the Local Safety Network connections.
Connect the BS-420 Ethernet 2 (J2) connection on the panel to Modbus Port 1 on the carrier and connect the BC-420 Ethernet 2 (J2) connection to Modbus Port 2. Verify that the BS-420 Ethernet 1 (J1) is connected directly to the BC-420 Ethernet 1 (J1). Note that these connections must match the configuration in the AS Configuration Tool.