Back before UL revision 9 came out the NetCom values read 0 to 7. 0 being the best and 7 the worst. After the UL Revision 9 changes the NetCon values changed to 5 to 7. 5 is the best 7 is worst. A NetCom 5 is needed to pass a fire inspection. The detailed explanation is below.
A Subscriber developed before the UL 864 9th Edition Compliant models calculate NetCon differently than the later. Edition 9 compliant Subscribers begin at firmware version 2.6+. The firmware version features typically follows all models. If another model is released with a version 2.6+ or higher, it would include the basic Subscriber functions as any other at that version with specific model variations added as needed. Version 2.6+ was designed to operate in a MultiNet environment and still be able to use NetCon 5 to indicate at least two unique paths exist in the current Routing Table all the way to the MultiNet Receiver/7705i.Earlier firmware than 2.6 was developed around the Single RF head end receiver concept, where they would report their NetCon as 0 if the #1 ID in the Routing Table was reporting a Link Layer/Level (LL) of 0.
RF Head End devices such as the 7003, 7703 or a 7170 IP-Link, are the only devices that can report LL as 0. A pre-V 2.6 Subscriber would report itself as a NetCon of 0, because the ID at the top of the list is a LL 0. In other words, if the #1 ID in the list is the single Stand Alone Receiver, it reports NetCon as 0.A V 2.6+ or higher does not report a NetCon of 0 with a LL as 0 in the #1 position. This prevents the reporting of NetCon 0 when a single IP-Link is at the top of the list. Two IP-Links are required to establish a NetCon of 5. Two IP-Links would in fact constitute two unique paths all the way to the 7705i. A third IP-Link would provide three unique paths, but NetCon would still be calculated as 5 adhering to the Edition 9 algorithm’s rules.