User`s guide

Introduction 1-4

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 plants can be accommodated with minimal, if

any, rewiring. This capability ensures that FTT-10A technology can be adapted

to both old and new projects, widening the potential market for FTT-10A-based

products. Finally, free topology permits FTT-10A systems to be expanded in the

future by simply 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

customer's perspective, keeps down the life cycle cost of the free topology network.

Loop Topology

Singly Terminated Bus Topology

Termination

Doubly Terminated Bus Topology

Star Topology

Mixed Topology

Figure 1.2 Typical Wiring Topologies Supported by the FTT-10A System

System expansion is simplified in another important way, too. Each FTT-10A

transceiver incorporates a repeater function. If a network segment grows beyond

the maximum number of transceivers or total wire distance, then additional

FTT-10A segments can be added by interconnecting transceivers using the

repeater function (figure 1.3). The repeaters will transfer LonTalk data between

the two segments, doubling the number of transceivers as well as the length of

wire over which they communicate. The repeater function permits an FTT-10A

network to grow as system needs expand, without retrofitting existing controllers

or requiring the use of specialized bridges. Note that systems requiring high

levels of network traffic may benefit from the use of LONWORKS routers which

forward packets only when necessary.