AIS (Automatic Identification System) is an automatic tracking system that broadcasts and receives information about vessels: GPS position, speed, course, vessel name, MMSI and dimensions. It operates on dedicated VHF channels 87B and 88B. Originally designed for large commercial ships, it is now widely used on recreational and small commercial vessels.

What is the difference between AIS Class A and Class B?

AIS Class A is mandatory for commercial vessels over 300 GT and transmits every 2-10 seconds at 12.5 watts. AIS Class B is for smaller vessels and transmits every 30 seconds at lower power (2 watts). For recreational vessels in Chile, Class B is the relevant standard. The practical difference: commercial ships receive your signal with a slight delay if you carry Class B, but they do see you.

What is the difference between an AIS receiver and a transponder?

An AIS receiver (receive-only) lets you see other AIS-equipped vessels on your screen, but they cannot see you. An AIS transponder transmits and receives: you see others and they see you. For navigation in areas with commercial traffic — such as port approaches, the Canal de Chacao, or the southern channels with wellboat traffic — a transponder is strongly recommended.

Does AIS replace radar or visual watch?

No. AIS only shows vessels equipped with AIS. Small boats, kayaks, rafts, fishing vessels, and debris do not have AIS and will not appear on your screen. Using AIS as your sole collision-avoidance system is a serious error. AIS complements radar and visual watch — it never replaces them.

Is AIS required in Chile?

For vessels over 300 GT in Chilean waters, Class A AIS is mandatory under the SOLAS Convention. For recreational and small commercial vessels there is no general legal requirement, but many insurers require or incentivise it. For navigation in areas with intensive commercial traffic — including the southern channels with wellboat traffic — I strongly recommend installing a transponder.

Marine AIS: What It Is and How It Works

Throughout my years at sea, I've seen two types of sailors: those who carry an EPIRB and those who don't. The first sleep better. The second, in the worst case, don't sleep anywhere again.

I don't say this to frighten anyone. I say it because the EPIRB is one of the most important safety pieces of equipment for navigation, and at the same time one of the least understood. Many people don't know exactly what it does, when it activates or how to register it. This guide exists to clear all that up.

What exactly is an EPIRB?

EPIRB stands for Emergency Position-Indicating Radio Beacon. It's an electronic device that, when activated in an emergency, transmits a distress signal to the international satellite system COSPAS-SARSAT.

That system is composed of low-orbit and geostationary satellites that receive the signal and retransmit it to ground stations. Those stations calculate the exact position of the beacon and alert the search and rescue coordination center (SAR) of the corresponding country — in our case, the Chilean Navy.

The result: within minutes or hours, rescue teams know where you are with meter-level precision.

"The EPIRB doesn't prevent accidents. But it can be the reason rescue arrives in time."

How Does an EPIRB Work?

An EPIRB works by transmitting a digital distress signal on the internationally reserved 406 MHz frequency — monitored continuously by the COSPAS-SARSAT satellite network. The signal contains a unique 15-digit hexadecimal identification code that tells rescuers exactly which vessel it's coming from.

Modern EPIRBs include an internal GPS receiver. This means the signal they transmit includes exact position coordinates with approximately 100-metre accuracy. Older models without GPS rely on the satellite calculating position via the Doppler effect, which takes longer and is less precise.

How an EPIRB works — step by step

Activation: the EPIRB activates — manually or automatically on water contact
Transmission: emits a digital signal on 406 MHz with identification code and GPS coordinates
Satellite detection: COSPAS-SARSAT satellites (LEO and GEO) capture the signal — detection time: ~90 min with LEO, near-instant with MEOSAR satellites
Ground station (LUT): the signal reaches a Local User Terminal that processes the position data
Coordination centre: the Mission Control Center alerts the SAR centre of the relevant country
Chilean Navy: receives the alert with position, vessel data and registered contacts — and mobilises rescue

There are two ways to activate an EPIRB: manually, when you press the activation button yourself, and automatically, when the device comes into contact with water. This second mode has saved the most lives — because in many maritime emergencies the crew has no time to activate anything.

Modern Category 1 EPIRBs have a hydrostatic release mechanism: if the vessel sinks, the device releases itself, floats, and activates automatically on contact with water. This works even if no one on board is conscious. The battery must sustain active transmission for at least 48 continuous hours.

Types of EPIRB

Category 1: Activates automatically on water contact (hydrostatic release). Most recommended for offshore navigation and the southern canals
Category 2: Manual activation only. Cheaper, but less safe — if you lose consciousness, it won't transmit
PLB (Personal Locator Beacon): Personal version, smaller, for each individual crew member. Does not replace the vessel EPIRB

Is the EPIRB mandatory in Chile?

The short answer is: it depends on the navigation category. The practical answer is: if you sail offshore or in remote areas, yes.

The Chilean Maritime Authority (Directemar) establishes equipment requirements by navigation category. For oceanic navigation, major coastal routes and remote areas like the southern canals, the EPIRB is a mandatory requirement for obtaining departure clearance. For sports vessels in coastal navigation, requirements vary by operating area.

My advice: don't sail without one, regardless of whether it's required. The cost of an EPIRB is minimal compared to the value of a life.

Common mistake

Many sailors buy an EPIRB but don't register it. An unregistered EPIRB is nearly useless: when it transmits, rescue teams have no information about the vessel or who is on board. Registration is mandatory and free.

How to register your EPIRB in Chile

Registration is done with the Chilean Navy through the nearest Harbour Master's office, or online through the Directemar system. You need the EPIRB's identification number (the 15-digit HEX code printed on the device), your vessel details and your personal contact information.

This registration means that when your EPIRB transmits, rescuers immediately know which vessel the signal corresponds to, how many people are typically on board, and who to call ashore. This information can significantly accelerate the rescue.

EPIRB maintenance

Battery: 5-year service life — must be replaced even if the device has never been used
Annual check: inspect the device's status indicator
Activation test: you can do a short test during the first 5 minutes of the first hour of each month (international protocol) — but notify the Navy beforehand
Update the registration if you change vessel or contact details
Storage: in an accessible location from deck, not in a locked drawer below

What happens if it activates accidentally?

Accidental activations are more common than people realize and have serious consequences. They can mobilize rescue resources unnecessarily, put other sailors at risk and generate significant costs. If your EPIRB activates by accident, switch it off immediately and notify the Navy or the nearest coast guard.

EPIRB vs PLB: do I need both?

This is a question I get often. The answer is that they are not the same and do not replace each other.

The vessel EPIRB is designed to identify and locate the vessel in distress. The PLB is a personal device that each crew member can carry on them — especially useful if someone falls overboard and drifts away from the vessel. In that case, the vessel's EPIRB is useless for that person.

For navigation in the southern canals or high-exposure areas, I recommend both: Category 1 EPIRB on the vessel, and one PLB per crew member.

Frequently Asked Questions about EPIRB

What is an EPIRB?

An EPIRB (Emergency Position-Indicating Radio Beacon) is a maritime emergency beacon that transmits a distress signal on 406 MHz to the COSPAS-SARSAT satellite system. It automatically alerts rescue centres with the vessel's exact position

How does an EPIRB work?

When activated, it transmits a digital signal on 406 MHz with a unique identification code and GPS coordinates. COSPAS-SARSAT satellites detect the signal and relay it to ground stations, which alert the Chilean Navy. The process takes between a few minutes and 90 minutes depending on satellite type

Is an EPIRB required in Chile?

Yes, for oceanic navigation, major coastal routes and the southern canals it is mandatory under the Maritime Authority (Directemar). For recreational vessels in coastal zones it depends on the authorised navigation area. Check with your local Harbour Master for your specific route

How long does an EPIRB battery last?

The battery has a 5-year standby life and must guarantee at least 48 hours of continuous active transmission. It must be replaced even if the device has never been used. The expiry date is printed on the device

What is the difference between an EPIRB and a PLB?

The EPIRB is for the vessel — it identifies and locates the boat. A PLB (Personal Locator Beacon) is a personal device carried by each crew member. They are complementary: if someone falls overboard and drifts away, only the PLB can locate that individual

Questions about your vessel's safety equipment?

I can review with you what safety equipment you need based on your route and type of navigation.

Consult the Captain →

Rodrigo Troncoso Peirano

Merchant Marine Captain with 30 years of experience in industrial fishing, offshore operations, and the fjords of Patagonia.

AIS: Automatic Identification System for Vessels