Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 40 of 118
This document is uncontrolled when printed.
1 The input remains OFF when it should be ON If the LED lights
The fault is not likely to be in the Input Optoisolator board. Check in
the following order until the problem is rectified:
Signalling side to ensure B12 is being switched to the input.
Possible faulty cable connection. Check connection at Input Opto
board and level crossing monitor case.
Possible damage cable. Check cable.
Possible faulty input on level crossing monitor. Replace level crossing
monitor.
If the LED remains extinguished
The fault is in the Input Optoisolator Board. Check in the following
order until the problem is rectified:
Possible Input Optoisolator circuit fault. Replace the Input
Optoisolator Board or the individual IC. A replacement IC may be
taken from an unused input.
Possible connection fault on the signalling side of the Optoisolator.
Check the voltage across the large 1 watt resistor (large brown
component between the 4N35 and green 8-way connector labelled
R1 to R32). If the voltage is less than 8 VDC, then the problem is in
the N24 connector. If voltage is present re-check Optoisolator Board.
2 The input remains ON when it should be OFF Re-check
by removing the corresponding 8-way connector.
If the LED remains illuminated. Check in the following order until
problem is rectified.
Possible short on output of 4N35. Replace the Input Optoisolator
Board or the individual IC. A replacement IC may be taken from an
unused input.
Possible damaged Cable. Test or replace cable.
Possible fault in Level Crossing monitor. Replace the level crossing
monitor.
If the LED is extinguished
Check the 8 way connector and external signalling circuit for a short.
3.5.5 Replacement Procedure
To remove a board: