Specifications

December 2008 Page 1–5
Chapter 1. Product Description
1
1.9 Framer Module
The Framer Module has four interfaces for bi-
directional links in the east, west, north, and south
directions. These correspond to transceiver 1-1, 1-
2, 2-1, and 2-2, respectively. This provides
communications along an T1/E1 line to the
network. All data and control information is
communicated by 2048 kbit/s serial streams
conforming to Mitel’s ST-BUS format.
The ST-BUS is a TDM serial bus. The serial
streams are divided into 125 µs frames of 32 8-bit
channels.
1.10 Power Supply Module
The Power Supply Module has several regulated
voltage supplies: +8 volts, -8 volts, +18 volts, -18
volts, and –30 volts. Each of these is connected to
the alarm system so that a failure is indicated on
the status LED and registers an alarm. The Power
Supply Module also contains the alarm status
LEDs for the major and minor alarms and the
external alert. In addition, each FOCUS module
provides onboard regulation of the power supply
voltages.
1.11 Modules for Protective
Relaying
1.11.1 Protective Relay Interface
Module
The Protective Relay Interface (PRI) Module
provides an interface for four independent bi-
directional transfer trip circuits. Either solid state
transistor (PRS) or mechanical contact outputs
(PRI) are available. The transfer trip circuits are
applicable for use in:
• Direct Transfer Trip
• Permissive Overreaching Transfer Trip
• Permissive Underreaching Transfer Trip
•Directional Comparison Blocking
•Directional Comparison Unblocking
•Secure Contact Status Transfer
There are separate guard and block outputs.
1.11.2 Pilot Wire Differential Relay
Interface
FOCUS provides a digital interface to two types
of pilot wire relays: HCB/HCB-1 and SPD. This
interface, along with a direct transfer trip (DTT)
channel, is included in a single DS0 channel of the
FOCUS system. This allows replacement of the
traditional metallic pilot wire and all associated
pilot wire monitoring devices. The result of this
replacement is an ideal pilot wire with nearly ideal
impedance and shunt capacitance.
A fiber optic link provides immunity from longi-
tudinally induced voltages and station ground
potential rise (GPR) and total electrical isolation.
The monitoring, conditioning, and protection
devices required for the metallic pilot wire, such
as isolating transformers, balancing resistors,
neutralizing and drainage reactors, and lightning
arresters, are eliminated from the system.
1.11.3 ANSI C37.94 (6NF) Module
The 6NF module is used to connect IEEE C37.94
compliant devices to the FOCUS multiplexer.
This eliminates the cost and interference problems
inherent with metalic circuits. The IEEE C37.94
standard was developed specifically to interface
protective relays to communications equipment
via fiber.
1.12 Tone and Voice Interfaces
FOCUS supports both voice and tone interfaces
for the electric substation via the Two-Wire
Modules and Four-Wire Modules. These modules
support the following applications:
•Intercom capability (ring down circuits)
• Remote extension capability
•Four-wire modems
•Two-wire modems
• Audio tones for relaying, etc.
• PBX extension lines
Each of these applications is discussed in the
following paragraphs.