The 51305072-400 is the non-CE version of the LCN I/O board for Honeywell's 5-slot and 10-slot chassis. This is the card where the LCN node address is set, and where the LCN A and B cables are connected. This version uses a slide switch for addressing.

TPN modules communicate with each other through interconnections of coaxial cable and fiber optic cable. There are two LCN cables for redundancy, Cable A and Cable B. Each cable must be routed separately and must be marked to indicate that it is Cable A or Cable B.

Cable A is marked with yellow and Cable B with green shrink-fit bands at the connectors. Each node on the TPN connects to both LCN Cable A and LCN Cable B through connectors called BNC tees. These connectors allow a node to be disconnected from the coaxial cable segment without disrupting communication among the other nodes. The tee connectors are part number 51190728-105 (this is not the same part number used for Data Hiway tee connectors).

An LCN can have up to seven coaxial cable segments—a central segment and up to six remote segments or remote nodes. The remote segments are connected to the central segment with LCN Extenders (LCNE2s/XLCNE2s). LCN Extenders use fiber optic cables that provide ground isolation and can run through hazardous areas to interconnect LCN coaxial cable bus segments.

For the CE version of this interface, see the 51305072-100.