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1. Introduction
The NEX7250 combines the RTK 725 Series Alarm Annunciator
installed in an IP rated enclosure
and self certified to comply with the international standard IEC 60079-15. The unit is self certified to
Ex nA [nL] IIC T4, with an ambient temperature range of -20
°
C to +50
°
C. The IP rated enclosure is
available in two forms: A wall mount IP55 rated enclosure or a panel mount IP54 rated enclosure.
The annunciator is manufactured from universal cells, each 60 x 60mm, which can be assembled in
an array to provide the number of rows and columns required to suit individual panel designs.
Each cell within the annunciator is able to contain either: - ONE large, TWO medium or FOUR small
alarm windows, which can be illuminated by “fit and forget” LED assemblies.
The assembled unit is fully field programmable which allows the user to enable a number of pre-
defined features to control the operation of the annunciator with regards to alarm sequence, horn
groups, common alarm groups or optional Modbus communications.
Selection of features is on a per channel basis with no special tools or programming knowledge
required. All programming is carried out from the front of the unit using the integral pushbutton /
programming module, which allows changes to be easily made during commissioning or at a later
date after the equipment has been installed.
Large and medium window version alarm cards are fully interchangeable within the annunciator, on
small window versions an additional card type is used for the 2
nd
pair of alarm channels but cards of
the same type remain fully interchangeable.
Reliability of operation is increased over conventional annunciators as each alarm card is fitted with
its own application specific integrated circuit (ASIC), which is capable of complete system control.
During initial power up one of the alarm cards will automatically act as a master controller with
regards to flash rates etc and in the event that this card fails or is removed another card will
automatically take over the role of master controller.
The standard unit is supplied with five integrally mounted common output relays, which are used to
provide 2 horn relay outputs, 2 group relay outputs and a multifunction relay output with
programmable function.
Additional options exist for more complex requirements including integrally mounted signal
duplicating relays on a per channel basis, bi-directional RS485 serial communications link and user
selectable time delays on each channel.
Accessibility for normal maintenance, LED changes, legend/filter changes and programming is
accomplished from the front of the panel without the use of special tools.
