Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 39 of 118
This document is uncontrolled when printed.
optoisolator circuit operation. B12 is only wired to that point to give quick
and handy access to a B12 test point to allow false feeding of inputs
during troubleshooting. If B12 is readily available elsewhere in the
location then this connection point does not need to be wired.
3.5.4 Troubleshooting
If there is no power supplied to the Input Optoisolator Board then all
inputs are read by the level crossing monitor as being 'off' (i.e. open
contact).
Two categories of failures are examined, multiple failures on one board
and single input failures. The 'Multiple Failure' section identifies failure
points that will most likely affect more than one circuit. The 'Single Input
Failure' section provides a comprehensive fault finding procedure of one
input circuit.
In the event that a multiple input failure is rectified by following the
multiple input failure procedure, the technician should then refer to the
single input failure section.
3.5.4.1 Multiple Input Failures On One Board
If the all of the inputs are permanently OFF then the fault is most likely to
be a power supply or connector problem. Check that:
 The B12 fuse for the indications is intact and the LXMON B12 bus
has the correct pins in place.
 The N12 connection to the Input Optoisolator board is intact.
 The cables from the level crossing monitor to the Input Optoisolator
board are intact and securely connected.
 The 5 VDC to GND test points both have 5 volts.
Multiple permanently ON failures are not likely to be a fault with the Input
Optoisolator board. Check the cables for damage, and loose or
damaged connections. Check Level crossing monitor for correct
operation and configuration.
If none of the above find the problem double check then replace the
Input Optoisolator board. If the problem persists then the level crossing
monitor is at fault and needs to be repaired or replaced.
3.5.4.2 Testing A Single Input
Each input may be corresponded into the level crossing monitor by
connecting a PC (with software) to channel B of the monitor and
ensuring that the reporting of changes mode is enabled. Now when any
input changes state it will be immediately reported to the PC.
Function test the inputs by forcing them on and off. If an input remains
OFF when it should be ON go to 1. If an input remains ON when it
should be OFF go to 2.