Specifications

RailCorp Engineering Manual — Signals — Equipment Manual

Cerberus Level Crossing Monitor Field Equipment Manual TMG E1261

Issued August 2012 UNCONTROLLED WHEN PRINTED Version 2.1

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.

2.5.5 Replacement Procedure

To remove a board:

• Unplug the 2 and 8 way green connectors by pulling them directly outward from the

board.

• The Cables are removed by unscrewing the two thumb screw fasteners on each

D25 connector, then pull the D25 plug directly outwards.

• The Optoisolator board is removed by twisting the board off the Klippon rail. Twist

by pulling the board on the 'thick' side of the Klippon rail whilst holding the board on

the 'thin' side of the Klippon rail.

To install a board: