Guide to PLBs & Satellite Messengers


Sometimes the call of the wild can take us to isolated and high-risk environments – whether it’s for adventure or because we’ve got a job to do! We always hope that things will go smoothly but being prepared with the right gear is essential.

Let’s consider our worst-case scenario and how we can best respond in an emergency situation. Distress beacons, like PLBs, are a reliable way to alert the authorities, but how exactly do these devices work? What are Satellite Messengers? Are they the same thing as a beacon and if not, how are they different?

We’re diving into the what, where, why and how, and have put together the answers to some of the most frequently asked questions.

A female hiker stands on the summit of a coastal mountain looking out to sea. There's a beautiful sunrise casting a hazy glow over the water and surrounding landscape, and the woman is wearing a brown canvas backpack with a ZOLEO messenger device attached to the top.

When adventure calls, it’s best to be prepared for an emergency with either a Satellite Messenger or PLB. Image: ZOLEO

There are 4 types of emergency devices:

  1. PLB – Personal Locator Beacons are used by adventurers and workers in remote high-risk environments.
  2. EPIRB – Emergency Position Indicating Radio Beacons are used in marine operations beyond 2 nautical miles from shore.
  3. ELT – Emergency Locator Transmitters are used in aircraft.
  4. Satellite Messenger – Similar to PLBs, these devices are used by adventurers, however, they operate via an independent/private network and allow for messaging in non-life-threatening situations.

EPIRBs and ELTs are specific to marine and air operations respectively and are designed to be installed and registered to the vessel.

PLBs and Satellite Messengers are commonly used for land-based activities and are designed to be worn on your person. They are used by an individual and are the focus of this article.

A hand holding an ACR PLB that's attached to the strap of a backpack.

All PLBs use the global COSPAS-SARSAT network. Image: ACR

What is a PLB?

A Personal Locator Beacon is designed to be used as a last resort when you have exhausted all other means of communication and you are in immediate and grave danger.

When we say grave danger, we mean a life or death situation. So, running out of fuel, or getting lost on the trail doesn’t warrant the use of a PLB.

Nowadays, most of these devices are GPS enabled and send out an emergency distress signal, including your GPS coordinates, to the relevant rescue authority.

The distress signal sent out by a PLB is 406 MHz. This special frequency is used just for search and rescue operations and communicates with a network of international military satellites called COSPAS-SARSAT. This network is made up of American, Russian, Canadian, and French satellites.

When you activate your beacon, your GPS location and the unique code relevant to your beacon will be transmitted to a rescue coordination centre via satellite, then the nearest rescue services will be notified.

Older model PLBs used the 121.5 MHz frequency however this is no longer detected by satellite and these models are no longer licensed for use. The Ocean Signal RescueMe PLB1 is an exception to this.

Close up of the Ocean Signal RescueMe PLB1 attached to a life vest. The side of a man's face takes up the right of frame.

The Ocean Signal RescueMe PLB1 is the smallest PLB currently available. Image: Ocean Signal

Ocean Signal RescueMe PLB1

The Ocean Signal RescueMe PLB1 uses three methods to communicate your location:

  • The 406 MHz network communicates to the satellites.
  • The 121.5 MHz homing capability is used to aid search and rescue with your location.
  • A high-density flashing strobe acts as a visual aid.

The RescueMe PLB1 is marketed towards kayakers, SUPers or recreational boaties. It’s proven popular with these water sport enthusiasts because although they aren’t suitable for marine use, they do work up to two nautical miles offshore. They also float and have a waterproof rating of 15-metres for 1-hour, so if you do happen to go overboard, your device will still operate – just be sure to have it clipped to you or your life vest!

Close up of a man's shoulder. He's wearing a black top and an ACR ResQLink PLB is attached to the strap of his backpack.

The ACR ResQLink View PLB has a digital display and shows GPS coordinates. Image: ACR


The ACR ResQLink 400 PLB and ResQLink View PLB both use the same three methods to communicate your location:

  • The 406 MHz network communicates to the satellites.
  • The 121.5 MHz homing capability is used to aid search and rescue with your location.
  • A high-density flashing strobe acts as a visual aid.

The ACR units differ from the Ocean Signal in their exterior casing, waterproof rating, and battery life. If you ever intend to reside in another country other than Australia the ResQLink will transition, however, other PLBs need to be re-coded and battery replacements can only be done within Australia.

The difference between these two ACR models is the additional technologies included with the ResQLink View. This unit has a digital display enabling you to read your own GPS coordinates and provides visual feedback during activation. Simply put, one is straight-up and the other is for techies!

The ACR ResQLink 400 PLB and ResQLink View PLB are popular with land-based outdoor enthusiasts – climbers, hikers, campers, cyclists, 4WDers, and lovers of action sports. They are also used in remote travel situations, be it for work or recreation.

A hand holding a smartphone with the SPOT Messenger app displaying a text. Text reads, "Hey babe, safe and sound! Everything's great."

A Satellite Messenger can be pre-programmed with messages for friends and family. Image: Spot

What is a Satellite Messenger?

Instead of using the government-run COSPAS-SARSAT system, Satellite Messengers operate via private or independently run networks that own commercial satellites.

Both SPOT and ZOLEO have partnered with the private network, GEOS International Emergency Response Coordination Center (IERCC). Once an SOS is activated, an alert is sent directly to GEOS IERCC who will notify the relevant authorities based on your GPS location and emergency situation.

Think of SPOT and ZOLEO like private companies that offer a more tailored service. This also means that you will have to pay some sort of plan or subscription fee.

A Satellite Messenger device gives you additional communication features and they’re ideal for people who want the option for something more than just a straight-up I’m in danger, send help!

Two kayakers - one stands in the foreground holding a SPOT Satellite Messenger and the other is in the background pulling his kayak near the shore.

SPOT Satellite Messengers are rugged yet compact and ideal for lightweight adventures. Image: Spot


Along with SOS, the SPOT Gen4 allows you to communicate with your friends and family when you’re out of range. You can pre-program custom messages that include your GPS coordinates to let them know that you’re okay, or that you need assistance but are not in serious danger. You can also show your tracking waypoints on your online account so your friends and family can monitor your progress.

The SPOT X 2-Way features the same SOS function but includes Bluetooth capabilities. By using the SPOT X app to connect the device to your smartphone you can exchange messages as you go instead of relying on pre-programmed texts and emails. The X 2-Way also allows you to navigate using the built-in compass and programmable waypoints.

Two hikers walk along a trail with green foliage around. They are both carrying rucksacks and the female hiker has a ZOLEO Satellite Messenger attached to her orange rucksack.

The ZOLEO device connects using an app on your smartphone. Image: Zoleo


Released onto the market early in 2020, ZOLEO’s Global Satellite Communicator raises the bar on Satellite Messenger devices. This device operates off the cellular and Wi-Fi networks and offers all the traditional satellite device features such as an SOS button and GPS navigation. But it’s the messaging capabilities that truly set it apart from its competitors. ZOLEO has partnered with the Iridium satellite network to enable messages anywhere on the planet! Using the free app on your smartphone, you can send and receive SMS, email, and app-to-app messaging – even when your ZOLEO device is turned off.

Their message functionality is next level and reflects a deep integration with the newest technologies so that the messaging experience remains familiar for the smartphone user. It comes with its own Australian SMS number and email which you can share with your contacts using the check-in button and unlike other satellite devices that require their antenna to be facing up, ZOLEO just needs a clear view of the sky.

Extreme close up of a thumb hovering over the SOS button on the RescueMe PLB1.

The Ocean Signal RescueMe PLB1 has a waterproof rating of 15-metres for 1-hour. Image: Ocean Signal

Does my PLB or Satellite Messenger need to float or be waterproof?

It depends on where you intend to use your device. If you’re going out on the water then one like the Ocean Signal RescueMe PLB1 is probably your best choice.

If you’re a hiker, cycle tourer, or heading off-road, then it’s unlikely that you’ll need your PLB or Satellite Messenger to have a high waterproof IP rating. Each device differs in its depth/timeframe and floatation capabilities, so go by what makes sense for what you’ll use it for.

Close up of an ACR ResQLink 400 PLB sitting on top of a life vest.

Always test the battery on your device before a trip and check the expiry date on PLBs. Image: ACR

What about the batteries?


  • How long batteries last before they expire depends on the type of battery used in the model of PLB that you have, but it varies between about 6 -10 years.
  • You will either have to get the battery replaced by an authorised battery replacement centre or send it back to the manufacturer when it’s time to replace the battery. If you have activated your device in an emergency situation, you need to replace the batteries before relying on your PLB again.
  • If you haven’t sent an alert, you will need to replace the battery before the expiry date listed which varies depending on the model. The price of replacing a battery will be different for each beacon but at the time of writing this article, the cost is between $150-$200.

Satellite Messengers

  • These generally use Lithium-ion batteries but that might vary depending on the brand. In terms of battery life, for example, the SPOT will last you about 13 days in SOS mode. So, you will need to keep batteries on hand when you are out in the field to replace them if necessary.
  • You can see the full battery performance table with all the information here on their website.

Image shows 2 computer monitors with a woman sitting looking at the screens. She's holding a PLB device and filling out the online registration form.

Registering your PLB is a simple and straightforward process.

What about fees, subscription services & registration?


  • You don’t have to pay any yearly subscription fees to use a PLB.
  • Your PLB will need to be registered/programmed with the Australian Maritime Safety Authority.
  • Registration is vital as your device will have a unique number. It’s also important to update your details if they have changed, and your trip information so in the event of a rescue, it’s easier for the emergency services to find you.

Satellite Messengers

  • Satellite Messengers do have a monthly or yearly subscription fee, depending on which payment plan you choose.
  • They require you to create an account with the relevant company, for example, SPOT or ZOLEO.
  • Once logged in, you are able to activate/register your device, choose a subscription plan and lodge your personal details.

A female hiker celebrates reaching the summit of a mountain with her arms out stretched in the air above her head. The view shows her towering over surrounding mountains, and water inlet and even scattered clouds. There are more clouds above and she's wearing a red backpack with a ZOLEO messenger device attached.

Purchase your emergency device from a reputable dealer. Image: ZOLEO

Does it matter if I buy it locally or overseas?

The country you purchase your unit in is the country it is programmed for, which is why it’s important to buy one locally. You won’t be able to register it in Australia unless you get the manufacturer to reprogram it with the Australian country code. There also may be an issue with whether the unit meets the Australian standards and requirements if you purchase it overseas.

While it may be tempting to grab a bargain from an international seller, it’s recommended by the Australian Maritime Safety Authority that you choose one that complies with Australian standards. You can also check out the list here of the PLBs that meet those Australian standards for reference.

A night time scene in the alps with a female hiker inside her hiking tent. The tent is illuminated by torch light and is glowing yellow.

Some devices have global coverage but they still must be registered in the country of purchase. Image: SPOT

Which PLBs & Satellite Messengers can be used internationally?

Every PLB uses the same global 406 MHz frequency and has approvals in multiple countries, so these are a great choice for overseas adventures.

These still need to be registered with the Australian authorities, and then if you need to activate it while travelling the signal is sent to the relevant authorities in your country of travel. The Australian authorities monitor your situation and liaise with the relevant international authorities to make sure you get out of trouble safely.

You also need to check with the manufacturer’s website for international use information and the relevant authority in the country you are visiting in case there are any restrictions.

ZOLEO is also connected to the Iridium satellite network giving them global coverage.

A lone male hiker holds a trekking pole as he reaches the summit of a coastal mountain at sunrise. He's wearing a backback with a ZOLEO messenger device attached to the top.

There are five main points to note when looking to purchase a PLB or Satellite Messenger. Image: ZOLEO

Summary of the main differences between a PLB & Satellite Messenger

  • Messenger device has a yearly fee, PLBs do not come with any fees.
  • All devices need to be registered with your personal details.
  • A PLB communicates with government-run satellites, a Satellite Messenger uses a private network.
  • A Satellite Messenger has a check-in and an SOS button. You will be able to link your progress to an online page as well, whereas a PLB has just one rescue function.
  • A PLB has a battery life of several years and replacements must be done by the manufacturer or an authorised centre. You can replace the batteries in your Satellite Messenger yourself and they need to be checked frequently, especially when in use.

Hopefully, we’ve managed to answer everything you wanted to know about PLBs and Satellite Messengers, and that you’re able to choose one with confidence. More information is available here and as always, Snowys is happy to help.

Happy adventuring and stay safe when you’re travelling off the beaten path.

Have you ever had to use a PLB or Messenger Device to be rescued? Let us know what your experience was. 

About the writer...

Joined back in December, 2016

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