Specifications

LONWORKS® LN-Series Network Communication and Interface Guide Technical Bulletin 11

Note: The recommended topology to use when designing a network is a bus

topology. Bus topologies are the easiest to troubleshoot and the maximum

wiring length in a bus topology is greater than in a free topology. See the

Channel Types section for detailed information about wiring lengths and

network cable considerations.

Free Topology

Free topology is a flexible wiring structure for communication channels that

include ring, star, loop and/or combination wiring structures. A free topology does

not have restrictions such as branching restrictions, stub length limits, device

separation requirements, or strict termination guidelines. The free topology

transmission specification has only two requirements that must be met for proper

system operation. The distance from each transceiver to all other transceivers and

to the termination must not exceed the maximum node-to-node distance. If

multiple paths exist (that is, a loop topology), then the longest path should be used

for calculations. The maximum total wire length is the total length of wire within a

segment. See the Network Cables section for detailed information about wiring

lengths and network cable considerations.

Network Termination

For free topology type networks (TP/FT-10 only), use Johnson Controls Part No.

NXM-TERM-FTT as the terminator for each free topology channel. We

recommend placing the terminator near the router for consistency.

Table 4: TP/FT-10 Free Topology Network Termination

Termination Requirements Johnson Controls Part No.

R1 = 52.3Ω, ±1%, 1/8 W

C1 = 100µF, ≥ 50 V

C2 = 100µF, ≥ 50 V

NXM-TERM-FTT

Figure 9: Free Topology