Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 85 of 118
This document is uncontrolled when printed.
Where :
000 is the Level Crossing ID number.
Generic, Generic Rd is the Location and Road name.
000.00 is the Kilometerage.
07/09/94 is the date
Refer to Section 7.3 Customising Generic expressions for details of the
allocation of Level Crossing ID numbers.
7.1.2.7 Boolean Expressions
Boolean expressions are combinations of logic operations on Boolean
variables. Boolean variables may have either of two values or states.
One of these states is called TRUE, ON, or 1. The other state is called
FALSE, OFF, or 0.
In relay terms TRUE is equivalent to UP, and FALSE is equivalent to
DOWN.
The level crossing monitor uses Boolean expressions to derive different
logic states of the level crossing in order to determine the whether or not
the level crossing is operating correctly.
There is a direct correspondence between relay circuits and Boolean
expressions. The Boolean expressions will be related to relay circuit as a
way of describing their operation.
7.1.2.7.1 AND Operator
The logical AND operation is represented by the "&" character.
Examples of logical AND operations are as follows: Either as relay logic
by:
A B C
or as a Boolean expression
C = A & B
C will only be true when both A and B are true.
7.1.2.7.2 OR Operator
The logical OR operation is represented by the "+"
character. Examples of logical OR operations are as
follows: Either as relay logic by: