March 19, 2021  The Alarm Button is now compatible with AIS MOB devices

The new update enables AIS PLBs support and offers an experimental feature of sounding Raymarine's alarms like anchor drift, MOB or low battery.

OceanSignal MOB1

The Alarm Button is a multifunctional device which can be used in different modes: as a MOB hardware button, or as an engine monitoring unit, or as a "music box" and audio alarm unit for a digital switching system.

In the MOB mode, when a user presses the connected button, the device turns on an audio alarm and sends an AIS MOB message to NMEA 2000. As a result, the MOB alert is triggered on all chart plotters in the NMEA 2000 network indicating the position and offering to navigate to the MOB point. This mode was designed to comply with offshore racing rules, which require having a hardware MOB button near the helm (and you also need it if you have an MFD without physical buttons or if your MFD is located near the chart table).

Today's update allows using the Alarm Button with personal AIS MOB devices like MOB1 from OceanSignal. The MOB1 is intended to be installed on a life-jacket (see the photo above) and automatically activates in the water. It sends an MOB signal with AIS protocol over VHF, and AIS receivers in the range up to 5 miles will get it.

If you have a single helmsman on watch and the MFD is located in the cockpit, the sleeping crew can miss the MOB signal from the MFD. In a rough sea, the range of MOB1 will be significantly reduced, and the signal can be lost in 20 minutes on a sailing yacht and much faster in the case of a motor boat.

The Alarm Button allows you to specify up to 5 different MMSI numbers with the YD:LIST command, for example:

	YD:LIST 226123100 226123101 226123102 226123103 226123104

If the AIS MOB message with any from specified MMSI is received by the Alarm Button, it will issue a sound alarm (event 1) in all modes, including engine monitoring mode and digital switching mode. To get the current configuration, enter the command without arguments.

To clear the list and turn this feature off, enter the following command:


This feature is a good addition to the Alarm Button. Many sailors are well-trained to sleep with MFD alarms, because they hear them too often (battery low, dangerous AIS targets, etc.). The loudspeaker with individual signal (even a voice message) in the saloon increases the safety and it will work even if the MFD is turned off for some reasons, but VHF with AIS or AIS receiver is on.

We also added experimental support of proprietary Raymarine alarms (PGN 65228). This PGN is not documented, it contains the alarm state in 4th byte (0 — cleared, 1 — active, 2 — dismissed) and the type in the 5th byte.

Modern Axiom chart plotters sends 115 (0x73) type in case of anchor drift alarm. You can configure the Alarm Button to issue the sound signal on this alarm, for example:

	YD:ALARM 5 115

Where the 5 is the number of Alarm Button's event (see the manual, it is numbered combination of visual and sound signals). You can configure all 28 events and link them to different Raymarine alarms (the unofficial list can be found in internet forums or find one yourself with CAN Log View). This feature can be used in all modes, but in the MOB button mode, use of event 1 is restricted.

To remove the alarm, enter the command:


or the command:


to remove all configured Raymarine alarms.

All the above sounds good, but Raymarine chart plotters also use type 115 when autopilot reaches the destination waypoint. In the Lighthouse update v3.8.97 (January 2019) they declared anchor alarm on SeaTalk NG as a new feature, but we tested the recent v3.11.42 and found that the alarm type remains the same. We decided to make this feature public in the hope, that in the next LightHouse updates the anchor drift alarm will get an individual number and that the Alarm Button will be more useful as a companion of RayMarine's MFD.

But this feature can be useful to create audio alarm on MOB event (type 38) issued by Raymarine Axiom. The command YD:EVENT (was previously disabled in the MOB mode) now works in all modes to support YD:ALARM command, but in the MOB mode the event 1 still can't be disabled.

Firmware update for Alarm Button (v1.05), is available at Downloads section.


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