Specifications

December 2008 Page 17–7
Chapter 17. Pilot Wire Interface (HCB/SPD) Module
17
wire resistance balancing resistors. The resistance
balancing is taken care of by the Pilot Wire
Interface Modules supplied by FOCUS.
You may, at some point, find it necessary to
remove one of the terminals of a three-terminal
line from service. When this occurs, you can use
the FOCUS Configuration Software (FCS) to
convert, or reconfigure, your three-terminal appli-
cation to a two-terminal application
When you convert a three-terminal system to a
two-terminal system, only the left side (from the
front of the chassis) HCB modules remain active.
All right side HCB modules become inactive.
Therefore, only the two terminals where the left
side HCB modules are communicating with each
other can operate as a two-terminal line. Looking
at Figure 17-12, for example, terminal A and
terminal C can operate as a two-terminal line, with
terminal B out of service. The terminal A to B and
terminal B to C connections, however, cannot be
set up for two-terminal line operation.
17.3 Installation
As with other FOCUS modules, we recommend
that you initially install and test the Pilot Wire
Interface Modules and rear interface modules in
“test” chassis (i.e., chassis that are not part of an
operating network). This way, you can quickly
perform the acceptance test without interfering
with a live network. Whether you are installing the
module in test chassis or chassis that are on line
in a network, use the installation procedure
described here.
Each Pilot Wire Interface Module occupies two
physical module slots in the FOCUS chassis. This
accommodates both the main board and the
module’s auxiliary board. The module requires
only one time slot on the T1/E1 line. The current
comparison information and a single transfer trip
function are encoded in this time slot. Before
installing the module and its interface, make sure
that:
• The FOCUS chassis is set up, energized,
and operational, with all necessary
common equipment (see Chapter 3)
Figure 17–12. HCB/FOCUS Three-Terminal Mapping.