CTI Products MCN RCD System Overview - Manual (Page 18)

MCN System Manual System Operation
CTI Products, Inc.
68-10833-120
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6. System Operation
This section describes the basic operation of both Comparator I/O Modules and
User Interface Modules in a comparator display system.
6.1 Monitoring and Control Operation
In an MCN system, the Comparator I/O Module accepts VOTE, RECEIVE,
DISABLE, and FAIL receiver status messages from the comparator and sends
them to a User Interface Module over the MCN network. User Interface Modules
then display the comparator status information on a console or PC.
Likewise, when a User Interface Module sends FORCE VOTE or DISABLE
commands, the Comparator I/O Module translates the commands and sends them
to the comparator.
MCN modules do not latch the FORCE VOTE or DISABLE controls to the
comparator. Any latching required for these signals must be provided by the user
interface device. For example, if using a console to control the DISABLE of a
receiver, the console switch has to be a latching switch, not a momentary, to keep
the DISABLE active after the button is released. The Remote Comparator
Display Software running on a PC does provide a latched DISABLE control so
that if the right mouse button is used to disable a receiver, the receiver will
remain disabled when the right mouse button is released. Pressing the right
mouse button a second time will re-enable the receiver.
Figure 2 shows a small system made up of three Comparator I/O Modules (the
CIBs) and one User Interface Module (the HIB). The PC can monitor and control
all three comparators from a single screen. For this example, assume that all three
comparators are Motorola Digitac comparators. When a receiver is force voted
from the PC, a FORCE VOTE message is generated by the RCD software and
sent to the CIB that is controlling that particular receiver. When the CIB receives
the FORCE VOTE message, it will drive the receiver’s VOTE output line to
signal the comparator that the receiver is being force voted. A similar process
occurs when a receiver is disabled from the PC.
Going the other direction, when the comparator detects that a receiver is active, it
will drive the RX input of the CIB. The CIB will then generate a RECEIVE
message and send it to the HIB so that the active receiver can be shown on the PC
screen. A similar process occurs when the comparator generates a Vote (driving
the CIB’s VOTE input) or a Fail (driving the CIB’s FAIL input) signal.