Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 75 of 118
This document is uncontrolled when printed.
6.1.2 Battery Test Outputs
Circuit sheet X14 shows the connections for the LX Monitor. The 8-
way Output Optoisolator terminals 1 & 8 are used to control the
remote battery test. The outputs switch to B12 to start a remote
battery test. Both outputs are used instead of only one to minimise
the risk of a false remote battery test failing the battery.
6.1.3 Battery Test Relay
The Battery Test Relay is a Q type, 12 volt QBCA1. The heavy duty
contacts of this relay are designed to carry a DC current of at least
30A for a minimum of 10 seconds on a 50% duty cycle. It is capable
of breaking a current of 30A without damaging the relay. The normal
duty contacts of this relay are rated 18V- 250V Switching AC
Inductive and 3 Amps continuous.
The heavy duty contacts place a load resistor across the level
crossing battery, see sheet X25. Two back contacts of this relay
disconnect the STORE 74 Battery Charger for the duration of the test.
The Battery Charger will draw a maximum of 3 Amps which is well
below the current capacity of these two parallel back contacts. A
front contact of this relay is also fed into the LX monitor for detection
purposes.
6.1.4 Non-Vital Timer
The Non-Vital timer circuit is shown on sheet X25 of the Standard
Circuits. The CUT OFF Timer is a delay ON timer set for 300
seconds. The unit is an industrial quality timer designed for critical
timing applications. It is used to stop the Battery test if the test
continues for significantly longer than the Battery test should last for.
The CUT OFF Timer de-energises the TEST CUT OFF Relay to
stop the test.
The CUT OFF Timer and the TEST CUT OFF Relay are tested by
the Level Crossing Monitor prior to a remote battery test.
The CUT OFF Timer is used as an independent control to prevent a
failure of the Level Crossing Monitor failing the Level Crossing
Battery which would be a serious safety risk.
6.1.5 Test Load Resistor
The test resistor is required to draw a test current from the Level
Crossing Battery. Current practice for testing level crossing batteries
is to operate the Test Switch for 2 minutes. This runs the crossing
with the AC supply disconnected. The Battery voltage is continually
monitored by the Store 74 Alarm card and gives a indication if the
battery voltage falls below a preset level.