HRK3-HB-7
V
IA
L
ITE
HD
3U
CHASSIS
H
ANDBOOK
8
4.3.2
Module bias feed
It is possible to provide a bias voltage from the modules to connected devices. Dependent on module type, this can be either internally
sourced from the module or provided via the
“Power Concentrator” connector J4. The current limit is dependent on module type fitted.
4.4
Alarm Management
The alarm strategy on the
ViaLiteHD
system caters for all levels of Alarm and Monitoring System complexity from simple module failure LED
indication, to local and remote end alarm notification and redundancy switching.
All modules provide an alarm output to the chassis backplane to indicate that the module is present and working correctly. The alarm is fail-
safe in that when a working module is withdrawn from the chassis an alarm is registered for that module position.
4.4.1
“Alarm Concentrator” 50way Connector J1
All module alarms are provided for the user on the 50 way “Alarm Concentrator” connector on the chassis rear panel. These outputs are
"open collector" outputs. There are also two analogue monitors per module position. Their function depends on the type of module fitted.
4.4.2
Connecting to an "open collector" output.
The alarm output pin should be connected to a suitable current source (a positive voltage via a 10kohm pull-up resistor is adequate). When
the module is in a working (non-alarm) state, the alarm output pin is short circuited to ground by the module. If the module enters an alarm
state, the alarm pin is released to a high impedance state and current is no longer drawn from the constant current source. In the case of a
positive voltage and pull-up resistor, the voltage on the alarm output pin will rise to indicate the alarm state. It follows that, if a module is
removed from the chassis, the alarm will be raised for that module position.
The capability of the open collector is dependent on the module that provides it.
The typical capability of the Open Collector/Drain is 50mA maximum current sink and 15V maximum voltage (Vext)
4.4.3
Summary Alarm
A summary alarm can be provided if an appropriate module is fitted in the 7HP slot (slot 14). This function can be provided by either of the
following modules
SNMP control module (automatic sensing of module presence)
Summary alarm relay module (manual setting of module presence)
If no module is fitted the summary alarm relay connections will all be open circuit.
If an appropriate module is fitted there is a volt free 3-
pin connection present on “Power Concentrator” Connector J4. The three connections
are Normally Open (NO), Common (COM) and Normally Closed (NC).
Condition 1 - Power applied to chassis, no alarms (i.e. normal condition)
Pin NO is open circuit
Pin NC is connected to COM
Condition 2 - Power removed from chassis and/or one or more module alarms (i.e. Alarm condition)
Pin NO is connected to COM
Pin NC is open circuit
RELAY_x
[1= normally closed, 2=common, 3=normally open]
Vext
Pull up
Resistor
Alarm
Ground
Internal to module External to module
