Module Descriptions
GARD 8000 SYS RFL Electronics
April 23, 2015 6-50 973.334.3100
6.11 MIDPLANE
There are two types of GARD 8000 midplanes, one for the 3U chassis (500415), and one for the 6U
chassis (500445). The midplanes are mounted in the chassis, such that, modules can be plugged in
from the front or rear of the chassis. This can be seen in Figures 6-1 and 6-2.
The midplane serves to distribute power and to interconnect all of the modules in the GARD 8000
chassis. There are three types of bussed signals that are connected to all modules, the Control bus, the
Logic bus and the Communication bus.
The Control Bus is used to configure modules and report status. The traffic on this bus is entirely
module-to-module and does not leave the chassis. No time critical data is passed over this bus.
The Logic Bus is used to transfer binary logic data between modules in the system in real-time. This
includes such information as whether an input is keyed or if an output should be energized. The data
on this bus may be brought out to the user, as with the inputs and outputs, or may remain module-to-
module.
There are two Communication Busses that are used to transfer user data to and from communications
I/Os. For example, for a relay to communicate with another relay it may send data to an RS-449
interface using a Comms Bus. This bus is not used to pass internal messages between modules in the
chassis.
In addition to these bus functions the midplane performs a number of other functions. The pins on the
connectors pass signals directly from the front module to the rear modules. Many modules connect
only to the bussed signals and do not use this feature. Others, such as relays, have dedicated I/O
modules that are installed directly behind the relay and interface with field wiring. There are also a
handful of lines that pass between adjacent modules. This may be used to allow modules to share
information or to expand the capabilities of a module. Most modules do not use this feature. There are
also a number of miscellaneous functions handled by the midplane.
6.12 CURRENT LIMIT MODULE
This optional module will limit the current output from the Station Battery when a carrier is present.
Unlike other I/O modules this module is located on the inside of the chassis. On the 3U chassis it is
located on the left hand side of the frame when viewed from the rear, next to the I/O System Module.
On the 6U chassis it is located below the Power Supply Board on the right hand frame when viewed
from the rear. For terminal block designations see the following page.
Table 6-23. Current Limiter Assemblies
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