8
Active Research Ltd 2022
Alarm Connections
•
The PRO-MUX-2 alarm functionality provides the vessel operator with two notification meth
-
ods when potential safety issues are detected during a voyage, allowing remedial action to be
performed. Each alarm can be configured to generate and send an NMEA 0183 ALR sentence
containing the relevant alarm details to the chosen output, plus the option of triggering the PRO-
MUX-2’s Alarm Relay output that could be connected to a variety of visual or audible alert devices.
Examples of the three alarm conditions that can be detected are detailed below.
Autoswitch ALARM:
• Multiplexers are often used to add redundancy to a system. GNSS receivers, for example, are
often duplicated for safety reasons, however combining data from two devices of the same type
in not recommended as the Listener will become confused. This is where the concept of the Au-
toswitch helps as it will only pass through data from one source/input, starting with the primary
data source/input and automatically switching over to the secondary (backup) source/input if the
primary data source is deemed no longer valid (e.g. due to equipment failure, cable failure, or in
the case of a GPS/VHF, antenna failure). This alarm will trigger when the Autoswitch has switched
to the secondary/backup data source, indicating that the system’s redundancy has been lost and
the issue affecting the primary data source should be investigated.
• 0183 output example:
• $MXALR,000655,002,PRO|<serial number of device>|Autoswitch:IN1>IN2
Data Overload ALARM:
• When routing and combining data from multiple inputs into an output, the chance that the vol-
ume of buffered data is higher than the bandwidth available to an output is high. In this scenario,
the PRO-MUX-2 will intelligently drop whole sentences, avoiding the issue of data corruption that
could confuse a Listening device, however random sentence data loss will occur. This will trigger
the Data Overload alarm, indicating that the routing configuration should be modified to intelligent
-
ly filter the data volume below what the output can cope with.
• 0183 output example:
• $MXALR,000655,001,PRO|<serial number of device>|Combine:Data overload
Low Voltage ALARM:
• The PRO-MUX-2 continuously monitors its own battery voltage supply. Should that supply drop
below a pre-set level, the Low Voltage alarm will be triggered, indicating that there is an issue with
the battery supply to the PRO-MUX-2, potentially giving forewarning of a total battery supply fail-
ure.
• 0183 output example:
• $MXALR,000655,001,PRO|<serial number of device>|Voltage Alert:PWR:10.2V
•
Note: the “<serial number of device>” value in the examples above will be replaced with the unique
serial number of the PRO-MUX-2 device that sent the alarm sentence, allowing the operator to
uniquely identify the unit.