What are Local Area Systems?

Personal Locator Beacons (PLB) operating on Local Area Systems use a combination of; 121.5MHz radio direction finding tone, VHF DSC distress alert (Mayday) on channels 70 & 16 and AIS GPS tracking, to alert the nearest vessel and provide updated location & tracking details to within +/- 1m.

Local Area Systems


  • 121.5MHz sends a radio direction finding tone that requires a bespoke receiver to detect and track the signal. This may be used as a standalone system; however, it is best utilized in addition to AIS, which provides a visual representation of the casualty with exact position coordinates updated every minute. 121.5MHz PLB’s are automatically activated and will alert all the vessels within the tone range e.g. the one you have just fallen off which is the greatest chance of a fast recovery.


  • The VHF DSC alerting function uses a DSC Distress alert (Mayday) on channel 70 and has a unique MMSI number for fast identification and tracking of multiple MOB casualties. Similar to the 121.5MHz, it works within a line-of-sight radius from where the signal is activated and communicates with all existing VHF DSC radios onboard any vessel. In addition, the GPS coordinates will be displayed and updated every 5 minutes to give you constant pinpoint tracking functionality.


  • AIS is the most accurate tracking and locating technology available which uses satellite systems, such as GPS, GLONASS & Galileo etc, to provide exact position coordinates of MOB casualties, which are continuously updated a minimum of 6 times every minute. As per the new international safety standards, RTCM and ETSI (draft), AIS cannot be used as an alerting function and is for location functioning only. AIS enables multiple MOB casualties to be located and tracked by all vessels, providing the greatest chance of survival in a MOB situation.    

The sMRT PLB range has been designed to meet the new international safety standards and uses a combination of 121.5MHz, VHF DSC and AIS GPS technologies in a single, compact, robust unit giving you and your crew the greatest chance of survival in the event of a MOB situation.

Want to find out more about the Local Area System?

If you would like to find out more about Local Area Systems, then don’t hesitate to get in touch with us today via info@mrtsos.com.

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