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Operation and Functional Description
LonWorks
®
Network Connection
The LonTalk
®
module has an FTT-10A Free Topology
Transceiver for network communication. The FTT-10A
transceiver network supports free topology wiring and will
accommodate bus, star, loop, or any combination of these
topologies. The module can be located at any point along
the network wiring. This capability simplifies system instal
lation and makes it easier to add nodes when required.
LonWorks
®
Network Cable
The LonWorks TP/FT-10 network requires Echelon quali
fied twisted-pair communication cables such as Belden
8471 or NEMA Level 4 cables. Other Echelon approved
equivalent cables may also be used depending on the ap
plication. The Belden 8471 or NEMA Level 4 cables are
rated for plenum use.
The network cable should be routed using best practices to
avoid induced noise. Do not route alongside power lines, or
in proximity to high voltage or high frequency devices, such
as ignition controls and variable frequency drives. The av
erage temperature of the wire must not exceed 131ºF
(55ºC).
Network Limits (Free Topology)
The LonWorks TP/FT-10 free topology network is limited
to a maximum of 64 nodes per segment. The maximum to
tal bus length and the maximum node-to-node length
is1640 ft. (500 m) for Belden 8471 or NEMA Level 4. Maxi
mum lengths are less for other smaller wire size cables.
Only one termination circuit module is required at any loca
tion along the network. Refer to Echelon LonWorks FTT-
Transceiver User's Guide for additional details.
Free Topology Networks
Free topology segments require a termination circuit for
proper performance. Only one termination circuit module
is required at any location along the network (see figure 2).
Network Limits (Doubly-Terminated Topology)
The LonWorks TP/FT-10 Doubly-Terminated topology
network is limited to a maximum of 64 nodes per segment.
The maximum total bus length is 5000 ft. (1524 m) for Bel
den 8471 or NEMA Level 4. Maximum bus lengths are less
for other smaller wire size cables. The maximum stub
length is 9.8 ft. (3 m). In many cases, this bus network is
connected in a daisy chain manner where the bus is wired
directly to each node, so stub length is zero.
Two termination circuit modules (37X75) are required for
each segment. One must be located at each end of the net
work (see figure 3).
LOOP
TOPOLOGY
Termination
STAR
TOPOLOGY
MIXED TOPOLOGY
(SINGLY TERMINATED)
Termination
Termination
Figure 2. Free Topology Networks
TerminationTermination
Figure 3. Doubly‐Terminated Topology
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