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

Test points next to each O/P connector are used to verify that +5 VDC is present for each

group of 16 circuits.

Wires from the signalling circuits are terminated on the 8-way (green) connectors. A

positive voltage is switched onto a terminal via a relay contact, push-button or switch.

The terminal on the Input Optoisolator Board can be likened to the positive terminal of a

non-vital relay coil. The return path for the signalling voltage is via the bottom 2-way

(green) connector (labelled 'N24'). This is a common return for all 32 inputs.

The 2-way (green) connector at the top of the board (labelled 'B24') is a test point for fault

finding. It does not perform any function in the 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.

2.5.4 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.

2.5.4.1 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 finds 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.

2.5.4.2 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.

1 The input remains OFF when it should be ON