These tracking transmitters are used in many safety situations, sea, air and personal. The beacons send out a distress signal that when it is detected by satellites and many such beacons also have a GPS position encoded into the distress signal. These can then be located by search and rescue aircraft and ground search parties on their way to aid whoever or whatever is in distress.

The main idea behind beacons such as the Epirb is to locate people within twenty four hours of receiving the distress signal as this is the time when they are most likely to be recovered alive. As time goes beyond that first twenty four hours; so the likelihood of the distressed being rescued will diminish.

ACR electronics make a range of equipment that is designed to help search and rescue teams locate aircraft, seacraft, and individuals who may be in distress. ACR's Global Fix 406 is designed to update a boat or ship's position every twenty minutes. It transmits on 406 MHz and contains a unique, digitally coded distress signal and 121 MHz SAR homing frequency. This instantly alerts search and rescue forces in the area that you are in distress and need help immediately. The Global Fix also contains a built in strobe which makes it easier for search and rescue teams to locate when visibility is poor.

The unit can be manually activated and is self buoyant which means that it does not need an external float collar. The casing is made from high impact plastic which is meant to be able to withstand UV rays, oil, sea water and raft packing. The set is battery operated and comes complete with a five year limited warranty. This unit weighs four and a half pounds and is operated by lifting up the switch, sliding it to the left and pushing it fully back and down breaking the tab, the unit becomes water activated once it is out of the bracket.

Epirbs are designed for different uses, the ACR float free 406 memory capsule is designed to be carried onboard with a record of a ship's data, rather like the little black boxes that are now carried by every aircraft. The 406 memory capsule is a lightweight object that has undergone testing in all kinds of conditions to assess its usefulness in real life situations.