Specifications

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2
2.1 Purpose
This chapter is designed to assist the engineer in
determining the exact bill-of-material required to
assemble a complete network of FOCUS nodes.
The reason for building such a network is to
provide an efficient method of transferring data
from one place to another. For the purpose of this
chapter, “data” is meant to include all types of
channels including voice, RS-232, 64K, protective
relay contact closures, etc. A node is defined as a
location containing some combination of dropped
data channels, inserted data channels, or pass-
through data channels between different
communication media. The latter will most
commonly be fiber optic cable pairs to either
digital microwave or a higher order fiber optic
multiplexer. In general, one FOCUS chassis is
required for every node on your system.
2.2 System Configuration
The nodes will generally be interconnected with
“links” of fiber optic cable pairs. Sometimes an
electrical cable is used for interconnecting two
chassis which are physically very close together.
Electrical cables are also used as links between
FOCUS and higher order multiplexers. Links are
required between any two nodes where data is
required to be transferred. It is not necessary to
have a direct link between every pair of nodes
containing the ends of a particular data channel.
This adds unnecessary expense to the installation
and, in most cases, is not possible. In many cases
data will be passed from the originating node
through one or more pass-through nodes before
reaching the destination node. Please refer to
Figure 2-2.
Figure 2–1. Sample FOCUS Network Topology.
A to B
A to D
B to D
B to C
Node D
Node BNode A
Node C
Node D
Node BNode A
Node C
Node D
Node BNode A
Node C
2. System Application and Ordering