Specifications

Page 17–6
FOCUS System Manual
Figure 17–11.
FOCUS/HCB Two-Terminal Application.
17.2.4 Three-Terminal Line
Application Considerations
The typical FOCUS to pilot wire connection is the
"two-terminal" application, as shown in Figure
17-11. In some cases, however, you may prefer a
"three-terminal" application as a cost saving
measure. A simplified three-terminal application
is shown in Figure 17-10.
A three-terminal-line application requires two
Pilot Wire Interface Modules at each line terminal.
At each terminal, you configure one module so
that it communicates with one of the remote
terminals and the other module so that it commu-
nicates with the other remote terminal. Figure
17-10 shows the functional connection of
channels for a three-terminal line. Each module at
each line terminal receives ac power frequency
information from each of the remote line
terminals. This information is then paralleled
together by the double-width interface module on
the rear of the chassis. Additional information is
communicated between the two modules via the
high speed data and control buses on the FOCUS
chassis.
When you are using FOCUS to provide the
communication path for the three-terminal HCB
application, there is no reason to apply the pilot
Figure 17–10. FOCUS/HCB Three-Terminal Application.