RFL 9300 RFL Electronics Inc.
August 9, 2001 4 - 12 (973) 334-3100
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4.2.28 COM MODE - COMMUNICATIONS MODE
Parameter #48 (COM MODE) controls the RFL 9300's hot standby communications mode. It
can be set to "AUTO" (automatic) or "MAN" (manual).
Whenever the RFL 9300 includes the "hot standby" redundant channel, the user is given the
choice of switching channels automatically every 12 hours or switching only by manual control.
(In both cases, the RFL 9300 will switch automatically whenever the channel in use fails).
If the two channels are considered to be of similar quality (equal availability, S/N ratio, etc), the
AUTO setting should be used. If one of the channels is preferred, the MAN setting should be
used. (An example of this is a privately-owned microwave backed up by a leased telephone
line.) Here, the user would command the RFL 9300 to work on the microwave channel all the
time. At regular intervals (like once a week), the RFL 9300 could be manually switched to the
leased-line channel for a while to monitor the status of the standby channel. COM MODE is not
displayed when the RFL 9300 is configured for 3-terminal operation.
Manual channel switching is controlled by Parameter #49 below.
4.2.29 ACT CHAN - ACTIVE CHANNEL SELECTION
Parameter #49 (ACT CHAN) allows the operator to command the RFL 9300 to work over a se-
lected channel. It can be set to either "CH 1" (Channel 1) or "CH 2" (Channel 2).
After making this setting, the RFL 9300 will communicate continuously over the selected chan-
nel, if the COM MODE parameter described above is set to "MAN." If the COM MODE parame-
ter is set to "AUTO," the channels will switch every 12 hours. This parameter can be set on
RFL 9300s equipped with two modems, two direct digital interface modules or two fiber optic
transceiver modules. It will not be displayed on units configured for 3-terminal operation.
4.2.30 G B4 TRP - GUARD BEFORE TRIP
Parameter #50 (G B4 TRP)
a. 2-terminal systems: Blocks trip until at least a total of 4 CCD or 8 WCM messages have
been received in succession from the remote station without a permissive trip being calculated
or until the Communications Controller signals that a clear channel has been established with
the remote terminal. Guard Before Trip is active when the RFL 9300 comes “on-line” following
initialization or after a communications outage. If a trip is calculated while the function is active
the count of received control signal messages will be reset to zero and the trip enable sequence
will be re-started.
b. 3-terminal systems: Blocks trip until at least a total of 8 control messages, either CCDs or
WCMs or a mix of these two messages, have been received in succession from the remote sta-
tions without a permissive trip being calculated or until the Communications Controllers signal
that a clear channel has been established with both remote terminals. Guard Before Trip is ac-
tive when the RFL 9300 comes “on-line” following initialization or after a communications out-
age. If a trip is calculated while the function is active the count of received control signal mes-
sages will be reset to zero and the trip enable sequence will be re-started.
G B4 TRP can be set to either ENABLE or DISABLE.
This parameter should be disabled if the ability to enable trip quickly after a communications
disruption takes precedence over the security afforded by this function.
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