A few decades ago they would have been dismissed as science fiction – but now most boats have one. Lindsay Wright looks into EPIRB technology, past and present.


Every time you walk past your EPIRB, it pays to spare a thought for the thousands of people who’ve dedicated their time, money and brain power to keep your bum covered when it’s out on the water – or up in the bush.
The first beacons took to the air (and went afloat) in the 1950s and transmitted an emergency signal on 121.5MHz – the international calling radio frequency monitored by all aeroplanes. These largely replaced the automated SOS radios which had been in use since the mid-1930s.



In November 1979, representatives from the USSR, USA, France and Canada got together in Leningrad and drew up a memorandum of understanding to form an international, not-for-profit, intergovernmental search and rescue organisation. They labelled the new outfit with an unwieldy acronym – COSPAS (Cosmicheskaya Sistyema Polska Avariynich Sudov) SARSAT (Search and Rescue Satellite Aided Tracking).
The plan was to install a network of satellites to receive distress messages sent by rescue beacons on 406MHz.
The first satellite – COSPAS-1 – was launched from the USSR in June 1982 and quickly earned its keep by helping rescue the pilot of a light plane which had crashed in the Canadian north. Using an experimental land user terminal (LUT) in Canada, rescuers were directed to the area and homed in using the 121.5MHz transmitter in his beacon to locate the badly-injured aviator. He survived his injuries and became the first COSPAS SARSAT success story.
Between then and December 2018, the satellite salvation service has helped save about 48,738 people worldwide.
Encouraged by its success, 45 other nations (including New Zealand) have signed the accord which is accepted as a model for global cooperation and is headquartered in Montreal, Canada.

And the little yellow beacons which were once an expensive rarity are now relatively cheap and commonplace on most boats. Weighing in at a few hundred grams, they come with a quick-release mounting bracket for easy installation near the hatch. As part of an offshore crew safety briefing, one crew-member should be delegated to make him/herself familiar with the instructions for using it and be responsible for grabbing the beacon in an emergency scenario.
Some people carry two beacons; an EPIRB (Emergency Position Indicating Rescue Beacon) and a PLB (Personal Locator beacon).
Last October, a New Zealand-bound yacht was swept by a big sea north of Cape Brett which carried away the liferaft mounted on the cabin top. Several tonnes of water landing on the boat compressed the fibreglass hull and popped the windows – so that the next waves filled the boat and she sank, like a lead-ballasted detergent bottle.
Three surviving crew were left dog-paddling miles from land in atrocious sea conditions but one of them activated his PLB and rescuers located them and winched them aboard a helicopter within a few hours. COSPAS SARSAT at work.
“To be living in a country that can throw so much resource without a moment’s thought at four people who need them the most … there must have been no hesitation when they got our Mayday and they were so prompt,” said survivor Bruce Goodwin. ‘’We feel so positive and honoured to live in such a country that cares for people.”

In 2018 the system’s satellites received 904 search and rescue alerts in New Zealand and were instrumental in 2,185 rescues.
Older beacons had the satellite capability but relied on an integrated 121.5MHz transmitter to direct rescue aeroplanes for close range location.
“There are stories of planes chasing trucks down the M1 in the UK because a beacon was accidentally turned on during loading,” says a National Rescue Coordination Centre spokesman, “but most new generation beacons have GPS transmitters in them. It sure takes the search out of search and rescue.” When the aero beacons were phased out in 2009, about 98% of false call-outs were eliminated.
Most commercial vessels are required to carry 406 beacons fitted with a hydrostatic release to self-deploy in an emergency. The hydrostatic release units work on a similar principal to aneroid barometers.
Inside them, a vacuum capsule made of very thin metal is compressed as the EPIRB (or vessel) sinks. At a preset depth/pressure (usually 4m) the vacuum capsule is pressurised enough to drive a sharp blade out to cut the retaining cord. The EPIRB pops to the surface and goes to work beaming signals to a passing satellite.
And satellites we have. COSPAS SARSAT operates five low-altitude earth orbit (LEOSAR) satellites, about 800–1000km above the planet, and about 40 medium altitude earth orbit satellites (MEOSAR) which were introduced in 2017 and orbit at about 20,000km. There are also nine GEOSAR satellites in geostationary orbit (they hold station over an appointed location over the earth).

In 2015 a joint-venture between Maritime New Zealand and the Australian Maritime Safety Authority built a satellite receiving station between Taupo and Rotorua to pick up signals from the about-to-be launched MEOSAR orbiters.
The longest time a user will be out of sight from a satellite is said to be two hours. “We talk about the ‘golden day’ period,” the NRCC spokesman explained. “It’s the 24 hours after an emergency event when distressed people are most likely to survive.” A GPS-equipped beacon will generally give rescuers a +/- 100m position finding accuracy – and often one far more precise.
And all at no cost to beacon users. All that’s required when buying an EPIRB is to call a toll-free number to register the 15, 22 or 30 digit ‘hex code’ on its casing. An appointed person’s phone number is included so, if the beacon is activated, rescue authorities can call it and verify the likely whereabouts of the user and make sure they’re not just partying at their marina berth. Hefty fines can be imposed for deliberate misuse of an EPIRB.


Once activated, the beacon sends off 0.5 second bursts of data, generally every 2.5 seconds, though this can vary slightly to prevent beacon signals from clashing. From there it takes less than a minute for the satellite to relay a distress message to an earth station (LUT).
EPIRBs retail for around $400 but, as with most technology, they are getting smaller and more efficient all the time.
Users are advised to test their EPIRB batteries once a month but in the process of testing my trusty (I believed) old Salcom MRB406 recently, I found that the battery was four years out of date. No problem. Safety Beacons NZ replaced the battery and updated the software for $240 (freight included).
A bargain at twice the price.