A Personal Locator Beacon (PLB) Explained
A Personal Locator Beacon (PLB) Explained is a personal electronic transmitter used to alert rescuers that there has been a life threatening man over board (MOB) situation with a need to be rescued. When activated, the PLB sends out a signal on either a 406MHz frequency or Local Area System using 121.5MHz, VHF DSC and/or AIS.
Often used in addition to other MOB protection equipment such as life jackets (PFD) or survival suits, PLB’s perform a critical function in the MASLOW of survival during an MOB situation.
What is 406MHz?
In the marine industry, 406MHz devices such as EPIRB’S and ELT’s have traditionally been used as a stand-alone solution for platforms such as aircrafts, vessels or platforms. Until recently, this system has typically been excluded from usage on individuals as it can only be manually activated, does not alert the nearest potential rescue vessel, i.e. the vessel you have just fallen off, has a location accuracy of +/- 100m and has an extend response time of up to 60 minutes, due to the way the system operates.
Once activated, the signal is detected by a satellite and sent to a Mission Control Centre (MCC) where it is decoded and forwarded to the nearest Rescue Coordination Centre (RCC). The RCC will then attempt to contact the registered details, which were provided upon purchase, to verify if it is a real MOB distress situation. On average, worldwide, this verification can take up to 60 minutes, as 99% of 406MHz activations are false, delaying the dispatch of the closest Search and Rescue forces. It is only once the distress alert has been verified at the RCC that a rescue plan is formulated and rescue assets are dispatched.
Important note: the 60 minute delay does not include the time for the rescue vessel to travel to the incident site.
What is Local Area Systems?
PLB’s operating on Local Area Systems use a combination of; 121.5MHzradio 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.
121.5MHz sends a radio direction finding tone that requires a bespoke receiver to detect and track the signal. This may be used as 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 change 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 cannotbe 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 an MOB situation.