USER’S GUIDE
Put Bar Code Here
74-2865—04
LONWORKS® Bus Wiring Guidelines

HONEYWELL CABLE 3252, 3253, 1061,

AK3797, AK3798, AK3799

INTRODUCTION

The Free Topology Transceiver (FTT) supports polarity
insensitive, free topology wiring. This frees the system
installer from wiring using a specific bus topology. T-tap, star,
loop, and mixed wiring topologies are all supported by this
architecture. Free topology wiring reduces the time and
expense of system installation by allowing the wiring to be
installed in the most expeditious manner. It also simplifies
network expansion by eliminating restrictions on wire routing,
splicing, and device placement.
A FTT network may comprise multiple segments (LONWORKS
Bus sections containing from one to sixty devices, each
device having a Neuron® ID to validate) separated by
physical layer repeaters or routers.
FTT networks are very flexible and convenient to install and
maintain, but it is imperative to carefully plan the network
layout and create and maintain accurate documentation. This
will aid in compliance verification and future expansion of the
FTT network. This will also minimize unknown or inaccurate
wire run lengths, node-to-node (device-to-device) distances,
node counts, total wire length, inaccurate repeater/router
locations, and misplaced or missing terminations.

APPLICATIONS

Free topology architecture allows the user to wire the control
devices with virtually no topology restrictions.
Unlike bus wiring designs, the FTT system uses a free
topology wiring scheme that supports T-tap, star, loop, mixed,
and/or daisy-chain (see Fig. 1). This design has many
advantages. First, the installer is free to select the method of
wiring that best suits the installation, reducing the need for
advanced planning and allowing last minute changes at the
installation site. Second, if installers have been trained to use
one style of wiring for all installations, free topology
technology can be introduced without requiring retraining.
Third, retrofit installations with existing wiring plans can be
accommodated with minimal, if any, rewiring. This capability
ensures that FTT technology can be adapted to both old and
new projects, widening the potential market for FTT based
products. Finally, free topology allows FTT systems easy
future expansion by tapping into the existing wiring where it is
most convenient to do so. This reduces the time and expense
of system expansion, and from the customers’ perspective,
keeps down the life cycle cost of the free topology network.
Fig. 1. Typical wiring topologies
supported by the FTT System.
TERMINATION
MODULE
TERMINATION
MODULE
DEVICE
DEVICE
DEVICE
TERMINATION
MODULE
TERMINATION
MODULE
DEVICE
DEVICE
DEVICE
MIXED
LOOP
DEVICE
DEVICE
DEVICE
DEVICE
DEVICE
DEVICE DEVICE
DEVICE
DEVICE
DEVICE
DEVICE DEVICE
DEVICE DEVICE
SINGLY TERMINATED
STAR
DEVICE DEVICE
DEVICE DEVICE
DEVICE
M12197