Configuration Definitions
14
NOTI•FIRE•NET™ PN 50257:E 7/5/01
Characteristic Impedance In a Point-to-Point Configuration
The wire segment of each point-to-point connection is a transmission line. The physical
construction of the twisted-pair cable used for a segment determines the characteristic impedance
of that segment. To minimize unwanted data reflections, never mix more than one brand name,
gauge, or type of wire within a point-to-point segment.
If a network employs point-to-point wiring only, a separate pair of wires must be run between each
node/repeater port (refer to Figure 7).
Figure 7 Point-To-Point Configuration
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Bus Configuration
A bus wiring configuration is defined as a twisted pair network with more than two nodes.
Terminating resistors are only needed for the first and last nodes of the bus configuration, all
other terminating resistors must be removed.
In a bus configuration, more than one node/repeater shares the same circuit (refer to Figure 8).
A fault anywhere along the bus will affect the rest of the nodes/repeaters on the bus. Because
of their inherent weakness, bus configurations are best employed for wiring between nodes/
repeaters local to each other (within the same cabinet or room).
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Wiring Distances Between Nodes On a Bus
In a bus configuration, data is shared between all ports on the twisted pair, thereby reducing the
allowable transmission distance to a maximum of 100 feet (refer to Table 2 through Table 4).
Figure 8 Bus Configuration (NFPA Style 4 Only)
Add this
segment for a
Style 7 system.
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