What are the different types of PLBs?

PLBs are predominantly known as beacons that transmit on the 406MHz frequency. PLBs can also be known as Maritime Survivor locating devices (MSLDs) and transmit on a range of different frequencies/technologies i.e. 121.5MHz, AIS and VHF DSC.

These frequencies/technologies can be utilised in the same device to have a PLBs/MSLDs transmit on multiple frequencies/technologies at the same time to increase the change of detection and location. Some current example of PLBs/MSLDs with multiple technologies are:

  • 121.5MHz and AIS – predominantly the 121.5MHz will be used for alerting, with the AIS used to track and locate
  • VHF DSC and AIS – similarly to the previous, VHF DSC will be used for alerting with the AIS used to track and locate
  • 406MHz and 121.5MHz – the 406MHz will be used for alerting and tracking, with the 121.5MHz used to locate once a rescue asset is in close proximity
  • 406MHz and AIS – 406Mhz used to alert worldwide with AIS used for local area tracking and locating
  • AIS only – AIS is predominantly a tracking and locating technology and does not always give an audible alarm when an AIS PLB/MSLD is activated.

PLBs/MSLDs can differ in type depending on the activity/job the user is undertaking. Examples of these are:

  • Some PLBs/MSLDs have what is known as an ATEX (ATmospheres EXplosible) or IECEX (International Electrotechnical Commission Scheme for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres) approval which allows them to be used in an environment with an explosive atmosphere.
  • Some PLB/MSLDs have Aviation (air worthiness) approval allowing them to be used in situations such as helicopter transit
  • Some PLBs/MSLDs have a greater water depth rating which allow them to be used in situations such as submarine escape
  • Some PLBs/MSLDs can be automatically activated whether that be with contact with water or on inflation of a PFD (personal flotation device). They can also be manually activated by the user. The type of PLB/MSLD will determine how the activation mechanism is operated.

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