Johnson Controls METASYS IFC-1010 Hardware Installation page 80

Operation By flanking each SLC loop device, creating zones with a pair of M500XJ
Fault Isolator Modules, each device is protected from opens and shorts on
all other zones.
containing addressable points. For instance, a short circuit on Zone 2 does
not affect Zone 1 and Zone 3. The isolator modules on either side of
Zone 2 open the SLC loop, Zone 1 still operates from power on Channel A
and Zone 3 operates from Channel B. Since the control panel is no longer
able to communicate with the SLC loop device on Zone 2, a trouble signal
is generated. When Style 7 is not required and some level of insulation is
still desired, the number of SLC loop devices between M500XJ modules
must not exceed 25.
The circuit illustrated in Figure 53 is a variation of an NFPA Style 6 SLC,
in this case, no T-tapping or branching is allowed. The rating and
characteristics are the same as for the Style 6 circuit.
80 Hardware Installation—Installing the IFC-1010/2020
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A zone is defined as one device or equipment enclosure