User's Manual

Weehawken Tunnel VHF Repeater System
User/Maintenance Handbook
Handbook N.-Weehawken_VHF Issue No:-A Date:-05/08/05
Page:-
48 of 75
6.2 Alarm/Monitor Shelf (80-231303)
6.2.1 Alarm/Monitor Shelf Description
The alarm shelf acts as an alarm concentrator for all the alarms in the system. Firstly, within
each shelf containing active components, the individually alarmed modules are ‘summed’
and presented to that shelves’ 9-way alarm connector as a volt-free relay contact pair. These
alarm contact pairs are wired to the krone block in the lower rack space and from there the
pairs are presented to the alarm shelf. At the alarm shelf the pairs are summed together to
form an overall system alarm. In this way a system alarm may be broken down to scrutinise
the shelf alarm and ultimately to the individual modules’ alarms.
This shelf has its own dedicated mains-driven power 12V DC supply.
As all the alarms in the system are ‘held closed loops’, should any power supply fail, the
main system alarm will be triggered.
6.2.2 Alarm/Monitor Shelf Technical Specification
PARAMETER SPECIFICATION
Operating voltage: 12V (floating earth)
Alarm output relay contacts:
Max. switch current: 1.0Amp
Max. switch volts: 120Vdc/60VA
Max. switch power: 24W/60VA
Min. switch load: 10.0µA/10.0mV
Relay isolation: 1.5kV
Mechanical life:
>2x10
7
operations
Relay approval: BT type 56
Connector details: 25 Way ‘D’ Connector
operational: :-10°C to +55°C
Temperature range
storage: :-40°C to +70°C