Installation guide

18 Introducing the Modbus Plus Network
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1.5.9 RR85 Repeater
The RR85 Repeater allows you to place more than 32 nodes on the
network and to increase the cable distance up to an additional 1500 ft
(450 m). It functions as an amplifier and signal conditioner to maintain
adequate signal levels between its two sections of the network. Up to
three Repeaters may be present in the message path between the
source and destination nodes. You can therefore join up to four sections
along a single linear path. Other configurations are possible and are
described later in this chapter.
Contact your Modicon distributor for information about models and
part numbers.
In addition to its use in extending the network, the Repeater can be
applied in plant environments that have high levels of electrical
interference. Repeaters at key points in the cable system can help to
maintain an excellent signal to noise ratio on the network.
The Repeater is provided with two ports for connection to the two
sections. It is counted as a physical node on each section. The
Repeater does not have a network address. It transparently passes
tokens and messages as they are received.
When Repeaters are used in dual-cable network layouts, one Repeater
must be positioned on each cable at the same point (between the same
pair of nodes) as on the other cable. Information is supplied in this
guidebook for installing Repeaters.