Specifications

RailCorp Engineering Manual — Signals — Equipment Manual
Cerberus Level Crossing Monitor Field Equipment Manual TMG E1261
© RailCorp Page 8 of 89
Issued August 2012 UNCONTROLLED WHEN PRINTED Version 2.1
The following Signal Engineering manuals provide additional information to this
document.
Cerberus Control Centre users guide
SCADA 2000 A/2.0 Technical manual.
1.3 Definitions
The following mnemonics are used in this document.
ADC Analogue to Digital Converter
IIO Individual Input Optoisolator
PCB Printed Circuit Board
SCADA Supervisory Control And Data Acquisition
VIO Vital Indication Optoisolator
1.4 Overview
1.4.1 Monitoring (How does it operate?)
Once every 0.25 seconds the Level Crossing monitor scans all of its inputs. It then
checks the pre-programmed relationships between its analogue inputs, digital inputs and
its digital outputs.
Through the use of the configuration data the level crossing monitor processes a number
of mathematical expressions (known as 'Boolean Expressions') to examine the
relationships. Each expression is the equivalent of a non-vital relay circuit. For more
information on Boolean Expressions consult the section on configuration data.
The pre-programmed relationships are customised for each particular level crossing.
However they are all based on a standard set of relationships that are discussed in this
section. Any specific expressions for a level crossing are contained in the expression file
for that particular level crossing.
The Level crossing monitor processes Boolean expressions with, internal intermediate
states and timer facilities to one second accuracy. Appendix A contains a sample set of
Boolean expressions that define the relationships for a standard level crossing.
The Level crossing monitor determines the number of lamps operating on each lamp
circuit. It then checks the number of lamps operating against the number that should be
operating as specified in the expression file. A lamp fault indication is provided when the
number of lamps detected is more than expected on any particular lamp circuit or 1 or
more lamps has failed on any circuit.
In normal operation the level crossing monitor will display two green LEDs which indicate
NO FAULT and NO WARNING. If a maintenance computer (either locally or remotely via
modem) is connected these two indications are combined to give a status of NORMAL on
the maintenance computer. If a FAULT occurs than the LED (on the level crossing
monitor front panel) for NO FAULT will extinguish, indicating that a FAULT has occurred.
If a WARNING occurs then the LED for NO WARNING will extinguish, indicating that a
WARNING has occurred.
The NO FAULT status indicates that the battery voltage is not low, no more than 1 lamp
is out, more lamps than expected have not been found, and no other fault detected by the